| Acyclic Graph EdgesOrient every edge so that the resulting directed graph has no cycle. | cses 1756 | not yet | — | — |
| AdvertisementThe largest axis-aligned rectangle fitting under the board heights. | cses 1142 | not yet | — | — |
| All Letter Subgrid Count IThe number of square subgrids containing every one of the `k` letters. | cses 3415 | not yet | — | — |
| All Letter Subgrid Count IIThe number of rectangular subgrids containing every one of the `k` letters. | cses 3416 | not yet | — | — |
| All Manhattan DistancesSum of the Manhattan distances over all point pairs. | cses 3411 | not yet | — | — |
| All PalindromesFor each position, the length of the longest palindrome ending there. | cses 3138 | not yet | — | — |
| All Subarray XorsEvery value that is the xor of some non-empty subarray, in increasing order. | cses 3233 | not yet | — | — |
| And Subset CountFor each `k` in `0..n`, the number of non-empty subsets whose bitwise and is `k`, modulo `10^9 + 7`. | cses 3141 | not yet | — | — |
| Another GameRemove one coin from each of a chosen non-empty set of non-empty heaps. | cses 2208 | not yet | — | — |
| ApartmentsMaximum number of applicants that can be matched to distinct apartments whose size is within `k` of the applicant's wish. | cses 1084 | not yet | — | — |
| Apple DivisionSplit the apples into two groups minimising the difference of total weights. | cses 1623 | not yet | — | — |
| Apples and BananasFor each combined weight `2..2k`, the number of apple/banana pairs with that total. | cses 2111 | not yet | — | — |
| Area of RectanglesTotal area covered by the union of axis-aligned rectangles. | cses 1741 | not yet | — | — |
| Array DescriptionNumber of arrays with values in `1..m`, adjacent values differing by at most 1, matching a description where `0` means unknown, modulo `10^9 + 7`. | cses 1746 | not yet | — | — |
| Array DivisionSplit the array into `k` consecutive pieces minimising the largest piece sum. Pieces may be empty; since `k ≤ n` this does not change the optimum. | cses 1085 | not yet | — | — |
| Beautiful Permutation IIThe lexicographically least permutation of `1..n` with no two adjacent elements differing by one, or `NO SOLUTION`. | cses 3175 | not yet | — | — |
| Binary SubsequencesA shortest bit string with exactly `n` distinct non-empty subsequences. | cses 2430 | not yet | — | — |
| Binomial Coefficients`a choose b` modulo `10^9 + 7`. | cses 1079 | not yet | — | — |
| Bit InversionsAfter each bit flip, the length of the longest run of equal bits. | cses 1188 | not yet | — | — |
| Bit StringsThe number of bit strings of length `n`, modulo `10^9 + 7`. | cses 1617 | not yet | — | — |
| Bit SubstringsFor each `k`, the number of non-empty substrings containing exactly `k` ones. | cses 2115 | not yet | — | — |
| Book ShopMaximum total pages of a set of books with total price at most `x`. | cses 1158 | not yet | — | — |
| Book Shop IIMaximum total pages buying at most `k i` copies of each book within budget `x`. | cses 1159 | not yet | — | — |
| Border Subgrid Count IFor each letter, the number of square subgrids whose border is entirely that letter. | cses 3417 | not yet | — | — |
| Border Subgrid Count IIFor each letter, the number of rectangular subgrids whose border is entirely that letter. | cses 3418 | not yet | — | — |
| Bouncing Ball CycleAfter how many steps the ball returns to its starting cell, and how many distinct cells it visits. | cses 3216 | not yet | — | — |
| Bouncing Ball StepsWhere the ball is after `k` steps, and how many times it has changed direction. | cses 3215 | not yet | — | — |
| Bracket Sequences INumber of balanced bracket sequences of length `n`, modulo `10^9 + 7`. | cses 2064 | not yet | — | — |
| Bracket Sequences IINumber of balanced bracket sequences of length `n` extending a given prefix, modulo `10^9 + 7`. | cses 2187 | not yet | — | — |
| Bubble Sort Rounds INumber of bubble sort rounds needed to sort the array. | cses 3151 | not yet | — | — |
| Bubble Sort Rounds IIThe array after `k` bubble sort rounds. | cses 3152 | not yet | — | — |
| Building RoadsFewest new roads making the road network connected, and such a set of roads. | cses 1666 | not yet | — | — |
| Building TeamsTwo-colour the pupils so that friends are on different teams, or `IMPOSSIBLE`. | cses 1668 | not yet | — | — |
| Bus CompaniesCheapest travel cost from city `1` to every city; one ticket lets you move between any two cities that company serves. | cses 3158 | not yet | — | — |
| Candy LotteryExpected maximum when `n` children each get a uniform value in `1..k`, to six decimal places. | cses 1727 | not yet | — | — |
| Chess TournamentGames so that each player plays exactly the number they asked for, with at most one game per pair. | cses 1697 | not yet | — | — |
| Chessboard and QueensCount placements of eight mutually non-attacking queens on free squares of an `8 × 8` board. The input is the reservation predicate on squares. | cses 1624 | not yet | — | — |
| Christmas PartyNumber of derangements of `n` gifts, modulo `10^9 + 7`. | cses 1717 | not yet | — | — |
| Coding CompanyNumber of ways to split the coders into teams whose total penalty, the sum over teams of the skill spread, is at most `x`, modulo `10^9 + 7`. | cses 1665 | not yet | — | — |
| Coin ArrangementFewest single-cell coin moves leaving exactly one coin per cell of a `2 × n` grid. | cses 2180 | not yet | — | — |
| Coin CollectorMaximum total of coins in the distinct rooms visited along some walk. | cses 1686 | not yet | — | — |
| Coin Combinations INumber of ordered sequences of coins summing to `x`, modulo `10^9 + 7`. | cses 1635 | not yet | — | — |
| Coin Combinations IINumber of multisets of coins summing to `x` (sequences counted up to order, represented by their sorted form), modulo `10^9 + 7`. | cses 1636 | not yet | — | — |
| Coin GridFewest row and column removals clearing every coin, and which lines to remove. | cses 1709 | not yet | — | — |
| Coin PilesPiles of `a` and `b` coins; a move removes `(1, 2)` or `(2, 1)`. Can both be emptied? Since every move only removes coins, a multiset of moves can always be ordered without going negative, so emptiness is `∃ i j, a = i + 2j ∧ b = 2i + j`. | cses 1754 | not yet | — | — |
| Collecting NumbersNumber of left-to-right passes needed to collect `1..n` in order from a permutation. | cses 2216 | not yet | — | — |
| Collecting Numbers DistributionFor each `k`, how many permutations of `1..n` need exactly `k` collecting rounds, modulo `10^9 + 7`. | cses 3157 | not yet | — | — |
| Collecting Numbers IIAfter each swap of two positions, the number of passes needed (see Collecting Numbers). | cses 2217 | not yet | — | — |
| Colored Chairs`n` chairs in a circle, `n` odd, each red or blue. Find neighbouring chairs of the same colour by asking at most 20 chair colours. | cses 3273 | no — interactive | — | — |
| Common DivisorsThe largest greatest common divisor of two elements at distinct positions. | cses 1081 | not yet | — | — |
| Company Queries IThe boss `k` levels above employee `x`, or `-1`. | cses 1687 | not yet | — | — |
| Company Queries IIThe lowest common boss of two employees. | cses 1688 | not yet | — | — |
| Concert TicketsCustomers arrive in order; each takes the most expensive remaining ticket not above their limit, or nothing (`-1`). | cses 1091 | not yet | — | — |
| Convex HullAll input points lying on the convex hull, in any order. | cses 2195 | not yet | — | — |
| Corner Subgrid CheckFor each of the first `k` capital letters, whether some subgrid of height and width at least two has that letter at all four corners. | cses 3360 | not yet | — | — |
| Corner Subgrid CountNumber of subgrids of height and width at least two whose four corners are black. | cses 2137 | not yet | — | — |
| Counting BishopsNumber of ways to place `k` bishops on an `n × n` board with no two on a common diagonal, modulo `10^9 + 7`. | cses 2176 | not yet | — | — |
| Counting BitsTotal number of one bits in the binary representations of `1..n`. | cses 1146 | not yet | — | — |
| Counting Coprime PairsNumber of position pairs whose values are coprime. | cses 2417 | not yet | — | — |
| Counting DivisorsThe number of divisors of each given integer. | cses 1713 | not yet | — | — |
| Counting GridsNumber of black/white `n × n` grids up to rotation, modulo `10^9 + 7`. | cses 2210 | not yet | — | — |
| Counting LCM ArraysNumber of positive arrays of length `n` with `lcm (a i) (a (i+1)) = k` throughout, modulo `10^9 + 7`. | cses 3169 | not yet | — | — |
| Counting NecklacesNumber of colourings of `n` pearls with `m` colours up to rotation, modulo `10^9 + 7`. | cses 2209 | not yet | — | — |
| Counting NumbersNumber of integers in `[a, b]` with no two equal adjacent decimal digits. | cses 2220 | not yet | — | — |
| Counting PathsFor each node, how many of the given paths pass through it. | cses 1136 | not yet | — | — |
| Counting PatternsNumber of positions where each pattern occurs in the string. | cses 2103 | not yet | — | — |
| Counting PermutationsNumber of permutations of `1..n` with no two adjacent elements differing by one, modulo `10^9 + 7`. | cses 1075 | not yet | — | — |
| Counting ReordersNumber of rearrangements with no two equal adjacent characters, counting rearrangements of equal characters separately, modulo `10^9 + 7`. | cses 2421 | not yet | — | — |
| Counting RoomsNumber of connected components of floor squares under side adjacency. | cses 1192 | not yet | — | — |
| Counting SequencesNumber of length-`n` sequences over `1..k` using every value at least once, modulo `10^9 + 7`. | cses 2228 | not yet | — | — |
| Counting TilingsNumber of domino tilings of an `n × m` grid, modulo `10^9 + 7`. A domino is an anchor cell plus an orientation (`true` = horizontal, covering the cell to the right; `false` = vertical, covering the cell below). | cses 2181 | not yet | — | — |
| Counting TowersNumber of ways to tile a `2 × n` tower with axis-aligned rectangular blocks of integer sizes, modulo `10^9 + 7`. A tiling is a set of blocks whose cells partition the tower. | cses 2413 | not yet | — | — |
| Course ScheduleAn order of all courses respecting every "a before b" requirement, or `IMPOSSIBLE`. | cses 1679 | not yet | — | — |
| Course Schedule IIThe lexicographically least topological order: finish course 1 as early as possible, then course 2, and so on. | cses 1757 | not yet | — | — |
| Creating OfficesMost offices placeable in a tree so that any two are at distance at least `d`. | cses 1752 | not yet | — | — |
| Creating StringsAll distinct rearrangements of a string, in alphabetical order, preceded by their count. | cses 1622 | not yet | — | — |
| Creating Strings IINumber of distinct rearrangements of a string, modulo `10^9 + 7`. | cses 1715 | not yet | — | — |
| Critical CitiesThe cities lying on every route from city `1` to city `n`, in increasing order. | cses 1703 | not yet | — | — |
| Cut and PasteRepeatedly cut the substring from `a` to `b` and append it at the end. | cses 2072 | not yet | — | — |
| Cycle FindingA closed walk of negative total length, printed as its vertices with the start repeated, or `NO`. | cses 1197 | not yet | — | — |
| Cyclic ArrayFewest cyclic segments each of sum at most `k`. | cses 1191 | not yet | — | — |
| De Bruijn SequenceA shortest bit string containing every bit string of length `n` as a substring. | cses 1692 | not yet | — | — |
| Dice CombinationsNumber of sequences of dice throws (values `1..6`) summing to `n`, modulo `10^9 + 7`. | cses 1633 | not yet | — | — |
| Dice ProbabilityProbability that `n` dice sum to a value in `[a, b]`, to six decimal places. | cses 1725 | not yet | — | — |
| Digit QueriesThe digit at 1-indexed position `k` of the infinite string `123456789101112…`. | cses 2431 | not yet | — | — |
| Distance QueriesDistance between two nodes of a tree. | cses 1135 | not yet | — | — |
| Distinct ColorsFor each node, the number of distinct colours in its subtree (root `1`). | cses 1139 | not yet | — | — |
| Distinct NumbersThe number of distinct values in a list. | cses 1621 | not yet | — | — |
| Distinct RoutesMaximum number of routes from `1` to `n` that pairwise share no teleporter, and such routes. | cses 1711 | not yet | — | — |
| Distinct Routes II`k` routes from room `1` to room `n` sharing no teleporter, using as few teleporters in total as possible, or `-1`. | cses 2130 | not yet | — | — |
| Distinct SubsequencesNumber of distinct non-empty subsequences, modulo `10^9 + 7`. | cses 1149 | not yet | — | — |
| Distinct SubstringsNumber of distinct non-empty substrings. | cses 2105 | not yet | — | — |
| Distinct Sums GridAn `n × n` grid where every value `1..n` occurs `n` times and the `2n` row and column sums are all different. | cses 3424 | not yet | — | — |
| Distinct Values QueriesNumber of distinct values at positions `a..b`. | cses 1734 | not yet | — | — |
| Distinct Values Queries IIPoint updates; whether all values at positions `a..b` are distinct. | cses 3356 | not yet | — | — |
| Distinct Values SplitsNumber of ways to cut the array into segments each of whose values are distinct, modulo `10^9 + 7`. | cses 3190 | not yet | — | — |
| Distinct Values SubarraysNumber of (position-distinguished) non-empty subarrays whose elements are pairwise distinct. | cses 3420 | not yet | — | — |
| Distinct Values Subarrays IINumber of subarrays with at most `k` distinct values. | cses 2428 | not yet | — | — |
| Distinct Values SubsequencesNumber of non-empty index subsets whose values are pairwise distinct, modulo `10^9 + 7`. | cses 3421 | not yet | — | — |
| Distinct Values SumSum, over every subarray, of the number of distinct values it contains. | cses 3150 | not yet | — | — |
| Distributing ApplesNumber of ways to give `m` identical apples to `n` distinguishable children, modulo `10^9 + 7`. | cses 1716 | not yet | — | — |
| Divisor AnalysisFor the number given by its prime factorisation, the count, sum and product of its divisors, each modulo `10^9 + 7`. | cses 2182 | not yet | — | — |
| Download SpeedMaximum flow from computer `1` to computer `n` with the connections as capacities. | cses 1694 | not yet | — | — |
| Dynamic ConnectivityThe number of components before the first event and after each edge insertion or deletion. | cses 2133 | not yet | — | — |
| Dynamic Range Minimum QueriesPoint updates and minima over positions `a..b`. | cses 1649 | not yet | — | — |
| Dynamic Range Sum QueriesPoint updates and sums over positions `a..b`. | cses 1648 | not yet | — | — |
| Edit DistanceFewest single-character insertions, deletions and replacements turning one string into another. | cses 1639 | not yet | — | — |
| Elevator RidesFewest elevator rides carrying everyone, each ride's total weight at most `x`. | cses 1653 | not yet | — | — |
| Empty StringNumber of ways to delete the string by repeatedly removing two equal adjacent characters, modulo `10^9 + 7`. | cses 1080 | not yet | — | — |
| Eulerian SubgraphsNumber of edge subsets in which every node has even degree, modulo `10^9 + 7`. | cses 2078 | not yet | — | — |
| Even Outdegree EdgesOrient every edge so that every node has even outdegree. | cses 2179 | not yet | — | — |
| Exponentiation`a^b` modulo `10^9 + 7`, with `0^0 = 1`. | cses 1095 | not yet | — | — |
| Exponentiation II`a^(b^c)` modulo `10^9 + 7`, with `0^0 = 1`. | cses 1712 | not yet | — | — |
| Factory MachinesLeast time `T` in which machines with per-product times `k_i` make `t` products in total; in time `T` machine `i` makes `⌊T / k_i⌋` products. | cses 1620 | not yet | — | — |
| Ferris WheelFewest gondolas, each holding at most two children with total weight at most `x`. | cses 1090 | not yet | — | — |
| Fibonacci Numbers`F n` modulo `10^9 + 7`, with `F 0 = 0` and `F 1 = 1`. | cses 1722 | not yet | — | — |
| Filled Subgrid Count IFor each letter, the number of square subgrids in which every cell holds that letter. | cses 3413 | not yet | — | — |
| Filled Subgrid Count IIFor each letter, the number of rectangular subgrids in which every cell holds that letter. | cses 3414 | not yet | — | — |
| Filling TrominosTile an `n × m` grid with L-trominoes; neighbouring squares carry the same letter exactly when they belong to the same piece. | cses 2423 | not yet | — | — |
| Finding a CentroidA node whose removal leaves components of at most `⌊n/2⌋` nodes. | cses 2079 | not yet | — | — |
| Finding BordersAll border lengths in increasing order, a border being a proper prefix that is also a suffix. | cses 1732 | not yet | — | — |
| Finding PatternsWhether each pattern occurs in the string. | cses 2102 | not yet | — | — |
| Finding PeriodsAll period lengths in increasing order, a period being a prefix whose repetition yields the string. | cses 1733 | not yet | — | — |
| Fixed-Length Paths INumber of (unordered) pairs of nodes at distance exactly `k`. | cses 2080 | not yet | — | — |
| Fixed-Length Paths IINumber of (unordered) pairs of nodes at distance between `k₁` and `k₂`. | cses 2081 | not yet | — | — |
| Fixed Length Walk QueriesWhether a walk of exactly `x` steps goes from `a` to `b`. | cses 3357 | not yet | — | — |
| Flight DiscountCheapest route from `1` to `n` when exactly one flight on it is charged at half price (rounded down). | cses 1195 | not yet | — | — |
| Flight Route RequestsFewest one-way flights making every requested route possible. | cses 1699 | not yet | — | — |
| Flight RoutesPrices of the `k` cheapest routes (walks, possibly repeating cities) from `1` to `n`, sorted. | cses 1196 | not yet | — | — |
| Flight Routes Check`YES` if every city reaches every other; otherwise `NO` and a pair `a b` with no route from `a` to `b`. | cses 1682 | not yet | — | — |
| Food DivisionFewest single-unit passes between neighbours around a round table turning the current amounts into the wanted ones. | cses 1189 | not yet | — | — |
| Forbidden CitiesWhether a route from `a` to `b` avoids city `c`. | cses 1705 | not yet | — | — |
| Forest QueriesNumber of trees inside a rectangle given by its corners `(y1, x1)`, `(y2, x2)` (1-based). | cses 1652 | not yet | — | — |
| Forest Queries IIToggle a square; count trees inside a rectangle. | cses 1739 | not yet | — | — |
| Functional Graph DistributionFor each `k`, the number of functional graphs on `n` nodes with exactly `k` connected components, modulo `10^9 + 7`. | cses 2415 | not yet | — | — |
| GCD SubsetsFor each `k`, the number of non-empty subsets whose greatest common divisor is `k`, modulo `10^9 + 7`. | cses 3161 | not yet | — | — |
| Game RoutesNumber of routes from level `1` to level `n` in an acyclic network, modulo `10^9 + 7`. | cses 1681 | not yet | — | — |
| Giant PizzaChoose toppings so that each family member gets at least one wish satisfied. | cses 1684 | not yet | — | — |
| Graph ColoringA proper colouring using the fewest colours, and the colour of each node. | cses 3308 | not yet | — | — |
| Graph GirthThe length of a shortest cycle, or `-1`. | cses 1707 | not yet | — | — |
| Graph Paths INumber of walks from node `1` to node `n` using exactly `k` edges, modulo `10^9 + 7`. | cses 1723 | not yet | — | — |
| Graph Paths IIMinimum total weight of a walk from node `1` to node `n` using exactly `k` edges, or `-1`. | cses 1724 | not yet | — | — |
| Gray CodeList all `2^n` bit strings of length `n` so that successive strings differ in exactly one bit. | cses 2205 | not yet | — | — |
| Grid Coloring IRecolour every cell of an `A`–`D` grid to a different letter so that no two side-adjacent cells share a letter, or report `IMPOSSIBLE`. | cses 3311 | not yet | — | — |
| Grid Coloring IIRecolour every cell of an `A`–`C` grid to a different letter so that no two side-adjacent cells match, or `IMPOSSIBLE`. | cses 3312 | not yet | — | — |
| Grid CompletionNumber of ways to complete the grid so that every row and column holds exactly one `A` and one `B`, modulo `10^9 + 7`. | cses 2429 | not yet | — | — |
| Grid Path ConstructionA path from `a` to `b` in an `n × m` grid visiting every square exactly once. | cses 2418 | not yet | — | — |
| Grid Path DescriptionCount the paths in a `7 × 7` grid from the upper-left to the lower-left square that visit every square once and match a 48-character pattern over `D U L R ?`. | cses 1625 | not yet | — | — |
| Grid Paths INumber of right/down paths from the upper-left to the lower-right square of an `n × n` grid avoiding traps, modulo `10^9 + 7`. Input: `trap[i][j]`. | cses 1638 | not yet | — | — |
| Grid Paths IINumber of right/down paths from `(1,1)` to `(n,n)` avoiding the traps, modulo `10^9 + 7`. | cses 1078 | not yet | — | — |
| Grid Puzzle IChoose exactly `a i` squares in row `i` and `b j` squares in column `j`. | cses 2432 | not yet | — | — |
| Grid Puzzle IIChoose exactly `a i` squares in row `i` and `b j` squares in column `j`, collecting as many coins as possible. | cses 2131 | not yet | — | — |
| Grundy's GameSplit a heap into two non-empty heaps of different sizes; the player moving last wins. | cses 2207 | not yet | — | — |
| Hamiltonian FlightsNumber of flight sequences from `1` to `n` visiting every city exactly once, modulo `10^9 + 7`. Parallel flights give distinct routes. | cses 1690 | not yet | — | — |
| Hamming DistanceSmallest number of differing positions between two of the given bit strings. | cses 2136 | not yet | — | — |
| Hidden IntegerFind a hidden `x` by asking whether `y < x`, in at most 30 questions. | cses 3112 | no — interactive | — | — |
| Hidden PermutationFind a hidden permutation of `1..n` by asking whether `a i < a j`, in at most `10^4` questions. | cses 3139 | no — interactive | — | — |
| High ScoreMaximum total of tunnel scores on a walk from room `1` to room `n`, or `-1` if unbounded. | cses 1673 | not yet | — | — |
| Hotel QueriesEach group takes the first hotel with enough free rooms (or `0` if none). | cses 1143 | not yet | — | — |
| Houses and SchoolsPlace `k` schools in houses minimising the total walking distance, each child going to the nearest school. | cses 2087 | not yet | — | — |
| Increasing ArrayYou are given an array of `n` integers. On each move you may increase one element by one. What is the minimum number of moves to make the array non-decreasing? Modelling choice: a sequence of unit increments from `xs` reaching `ys` exists iff `xs ≤ ys` pointwise, and its length is `Σ (ys[i] - xs[i])`. We take that as the definition of "moves", so the answer is the minimum of `cost xs ys` over reachable non-decreasing `ys`. | cses 1094 | not yet | — | — |
| Increasing Array IILeast total change, up or down, making the array non-decreasing. | cses 2132 | not yet | — | — |
| Increasing Array QueriesMinimum unit increments making positions `a..b` non-decreasing (see Increasing Array). | cses 2416 | not yet | — | — |
| Increasing SubsequenceLength of a longest strictly increasing subsequence. | cses 1145 | not yet | — | — |
| Increasing Subsequence IINumber of non-empty index subsets whose values are strictly increasing in index order, modulo `10^9 + 7`. | cses 1748 | not yet | — | — |
| Intersection PointsNumber of points where a horizontal and a vertical segment meet. | cses 1740 | not yet | — | — |
| Inverse InversionsA permutation of `1..n` with exactly `k` inversions. | cses 2214 | not yet | — | — |
| Inverse Suffix ArrayA string over `a`–`z` whose suffix array is the given permutation, or `-1`. | cses 3225 | not yet | — | — |
| Inversion ProbabilityExpected number of inversions when position `i` holds a uniform value in `1..r_i`, to six decimal places. | cses 1728 | not yet | — | — |
| Inversion SortingSort a hidden permutation by reversing subarrays; after each reversal you are told the number of inversions, and you win when it reaches zero. At most `4n` reversals are allowed. | cses 3140 | no — interactive | — | — |
| InvestigationFor routes from `1` to `n`: the minimum price, the number of minimum-price routes modulo `10^9 + 7`, and the fewest and most flights on a minimum-price route. | cses 1202 | not yet | — | — |
| Josephus Problem IChildren `1..n` in a circle; every other child is removed. The removal order. | cses 2162 | not yet | — | — |
| Josephus Problem IIChildren `1..n` in a circle; repeatedly skip `k` and remove the next. The removal order. | cses 2163 | not yet | — | — |
| Josephus QueriesWith `n` children in a circle and every second child removed, who is removed `k`-th. | cses 2164 | not yet | — | — |
| K Subset Sums IThe `k` smallest sums over all `2^n` subsets. | cses 3108 | not yet | — | — |
| K Subset Sums IIThe `k` smallest sums over the subsets of exactly `m` elements. | cses 3109 | not yet | — | — |
| K Subset XorsThe `k` smallest subset xors, counting each of the `2^n` subsets separately. | cses 3192 | not yet | — | — |
| Knight Moves GridFor every square of an `n × n` board, the least number of knight moves to the top-left corner. | cses 3217 | not yet | — | — |
| Knight Moves QueriesFewest knight moves from `(x, y)` to `(1, 1)` on an infinite board. | cses 3218 | not yet | — | — |
| Knight's TourNumber the squares `1..64` in the order a knight visits them, starting at column `x`, row `y`. | cses 1689 | not yet | — | — |
| Knuth DivisionRepeatedly split a piece into two; each split costs the sum of that piece. The least total cost of splitting the array into single elements. | cses 2088 | not yet | — | — |
| K-th Highest ScoreTwo countries each have `n` distinct scores. Asking for the `i`-th highest score of one country, find the `k`-th highest overall in at most 100 questions. | cses 3305 | no — interactive | — | — |
| LabyrinthA shortest path from `A` to `B` through floor squares, as a move string. | cses 1193 | not yet | — | — |
| Letter Pair Move GameMove adjacent letter pairs into the two empty boxes until every `A` precedes every `B`; the output lists the configuration after each turn. | cses 2427 | not yet | — | — |
| Line Segment IntersectionWhether two segments share at least one point. | cses 2190 | not yet | — | — |
| Line Segments Trace IFor each integer `x` in `0..m`, the highest point on any segment from `(0, y₁)` to `(m, y₂)`. | cses 3427 | not yet | — | — |
| Line Segments Trace IIFor each integer `x` in `0..m`, the highest point on any segment covering `x`, or `-1`. | cses 3428 | not yet | — | — |
| Lines and Queries IAdd lines `a x + b`; report the largest value of any added line at `x`. | cses 3429 | not yet | — | — |
| Lines and Queries IIAdd lines active on a range; report the largest value of any active line at `x`, or `NO`. | cses 3430 | not yet | — | — |
| List of SumsRecover a list from the multiset of its pairwise sums. | cses 2414 | not yet | — | — |
| List RemovalsRemove the element at the given (current) position each time; report the removed elements. | cses 1749 | not yet | — | — |
| Longest Common SubsequenceLength of a longest common subsequence of two arrays, and one such subsequence. | cses 3403 | not yet | — | — |
| Longest Flight RouteA route from `1` to `n` in an acyclic flight network visiting the most cities. | cses 1680 | not yet | — | — |
| Longest PalindromeA longest palindromic substring. | cses 1111 | not yet | — | — |
| MST Edge CheckFor each edge, whether some minimum spanning tree contains it. | cses 3407 | not yet | — | — |
| MST Edge CostFor each edge, the least spanning tree cost among trees containing that edge. | cses 3409 | not yet | — | — |
| MST Edge Set CheckFor each set of edges, whether some minimum spanning tree contains all of them. | cses 3408 | not yet | — | — |
| Mail DeliveryA closed route from crossing `1` using every street exactly once (an Eulerian circuit). | cses 1691 | not yet | — | — |
| Maximum Average SubarraysFor each end position, the length of the longest subarray ending there with the greatest average. | cses 3301 | not yet | — | — |
| Maximum Building IThe largest rectangle of tree-free squares. | cses 1147 | not yet | — | — |
| Maximum Building IIFor every building size, the number of placements avoiding all trees. | cses 1148 | not yet | — | — |
| Maximum Manhattan DistancesAfter each point is added, the largest Manhattan distance between two of them. | cses 3410 | not yet | — | — |
| Maximum Subarray SumLargest sum of a non-empty contiguous subarray. | cses 1643 | not yet | — | — |
| Maximum Subarray Sum IILargest sum of a contiguous subarray whose length is between `a` and `b`. | cses 1644 | not yet | — | — |
| Maximum Xor SubarrayLargest xor of a contiguous subarray. | cses 1655 | not yet | — | — |
| Maximum Xor SubsetLargest xor of a subset of the elements. | cses 3191 | not yet | — | — |
| Meet in the MiddleNumber of index subsets whose values sum to `x`. | cses 1628 | not yet | — | — |
| Message RouteA route from computer `1` to computer `n` through the fewest computers. | cses 1667 | not yet | — | — |
| Mex Grid ConstructionAn `n × n` grid where each cell holds the least non-negative integer absent from the cells to its left in its row and above it in its column. | cses 3419 | not yet | — | — |
| Mex Grid QueriesThe value at square `(y, x)` of the infinite mex grid. | cses 1157 | not yet | — | — |
| Minimal Grid PathLexicographically least string read along a right/down path from the upper-left to the lower-right square of a letter grid. | cses 3359 | not yet | — | — |
| Minimal RotationThe lexicographically least rotation of the string. | cses 1110 | not yet | — | — |
| Minimizing CoinsFewest coins (with repetition) from the given denominations summing to `x`, or `-1`. | cses 1634 | not yet | — | — |
| Minimum Cost PairsFor each `k`, the least total `|a - b|` over `k` disjoint pairs. | cses 3402 | not yet | — | — |
| Minimum Euclidean DistanceThe square of the least distance between two distinct points. | cses 2194 | not yet | — | — |
| Missing Coin SumThe smallest positive sum not obtainable from a sub-multiset of the coins. | cses 2183 | not yet | — | — |
| Missing Coin Sum QueriesSmallest sum not obtainable from coins `a..b` (see Missing Coin Sum). | cses 2184 | not yet | — | — |
| Missing NumberGiven `n - 1` distinct numbers from `1..n`, find the one that is missing. The input object is the list of given numbers; `n` is its length plus one. | cses 1083 | not yet | — | — |
| Money SumsAll positive sums obtainable from a sub-multiset of the coins, in increasing order. | cses 1745 | not yet | — | — |
| Monotone SubsequencesA permutation of `1..n` whose longest monotone subsequence has exactly `k` elements. | cses 2215 | not yet | — | — |
| Monster Game IKill a subset of the monsters, always including the last; killing monster `i` with current skill factor `f` costs `s i * f`, and afterwards the skill factor becomes `f i`. The least total time. | cses 2084 | not yet | — | — |
| Monster Game IIKill a subset of the monsters, always including the last; killing monster `i` with current skill factor `f` costs `s i * f`, and afterwards the skill factor becomes `f i`. The least total time. | cses 2085 | not yet | — | — |
| MonstersEscape to the boundary so that at every time `t` no monster could be on your square (monsters move at most one step per turn and may wait). | cses 1194 | not yet | — | — |
| Mountain RangeGlide from `a` to `b` when `a` is taller than `b` and than everything between. Maximum number of mountains on a route. | cses 3314 | not yet | — | — |
| Movie FestivalMaximum number of movies one person can watch entirely. | cses 1629 | not yet | — | — |
| Movie Festival II`k` club members; maximum total number of movies watched entirely, each member watching pairwise non-overlapping movies. | cses 1632 | not yet | — | — |
| Movie Festival QueriesMaximum number of pairwise compatible movies entirely inside the time window `[arrive, leave]`. | cses 1664 | not yet | — | — |
| Moving RobotsExpected number of empty squares of an `8 × 8` board after every robot takes `k` uniformly random steps, to six decimal places. | cses 1726 | not yet | — | — |
| Multiplication TableThe middle value of the `n × n` multiplication table sorted in increasing order. | cses 2422 | not yet | — | — |
| Nearest Campsites IThe largest distance from a free campsite to its nearest reserved campsite. | cses 3306 | not yet | — | — |
| Nearest Campsites IIFor each free campsite, the distance to its nearest reserved campsite. | cses 3307 | not yet | — | — |
| Nearest ShopsFor each city, the distance to the nearest *other* city with a shop, or `-1`. | cses 3303 | not yet | — | — |
| Nearest Smaller ValuesFor each position, the nearest position to its left with a smaller value (1-based), or 0. | cses 1645 | not yet | — | — |
| Necessary CitiesThe articulation points: cities whose removal disconnects some other pair. | cses 2077 | not yet | — | — |
| Necessary RoadsThe bridges: roads whose removal disconnects some pair of cities. | cses 2076 | not yet | — | — |
| Nested Ranges CheckFor each range: does it contain another range, and is it contained in another range. | cses 2168 | not yet | — | — |
| Nested Ranges CountFor each range: how many other ranges it contains, and how many contain it. | cses 2169 | not yet | — | — |
| Network BreakdownThe number of components after each connection breaks. | cses 1677 | not yet | — | — |
| Network RenovationFewest new connections making the tree survive any single connection failure, that is, making the graph bridgeless. | cses 1704 | not yet | — | — |
| New Flight RoutesFewest new one-way flights making the whole network strongly connected. | cses 1685 | not yet | — | — |
| New Roads QueriesAfter how many days two cities are first connected, or `-1`. | cses 2101 | not yet | — | — |
| Next PrimeThe smallest prime strictly greater than each given number. | cses 3396 | not yet | — | — |
| Nim Game IRemove any number of sticks from one heap; the player taking the last stick wins. | cses 1730 | not yet | — | — |
| Nim Game IIRemove one, two or three sticks from one heap; the player taking the last stick wins. | cses 1098 | not yet | — | — |
| Number of Subset XorsHow many distinct values arise as the xor of a subset. | cses 3211 | not yet | — | — |
| Number SpiralFor each query `(y, x)` report the number at row `y`, column `x` of the spiral. The statement defines the spiral by a picture. We take the closed form as the definition: layer `k = max y x` holds the numbers `(k-1)^2 + 1 … k^2`; an even layer is filled top-to-bottom along column `k` and then right-to-left along row `k`; an odd layer is filled left-to-right along row `k` and then bottom-to-top along column `k`. | cses 1071 | not yet | — | — |
| One Bit PositionsFor each distance `k`, the number of position pairs `i - j = k` that both hold a one. | cses 2112 | not yet | — | — |
| Palindrome QueriesCharacter updates; whether the substring from `a` to `b` is a palindrome. | cses 2420 | not yet | — | — |
| Palindrome ReorderReorder the letters of a string into a palindrome, or report that none exists. | cses 1755 | not yet | — | — |
| Parcel DeliveryCheapest way to send `k` parcels from city `1` to city `n` respecting route capacities, or `-1`. This is a minimum-cost flow of value `k`. | cses 2121 | not yet | — | — |
| Path QueriesNode value updates; sum of values on the path from the root `1` to a node. | cses 1138 | not yet | — | — |
| Path Queries IINode value updates; maximum value on the path between two nodes. | cses 2134 | not yet | — | — |
| Pattern PositionsFirst (1-based) occurrence position of each pattern, or `-1`. | cses 2104 | not yet | — | — |
| Permutation InversionsNumber of permutations of `1..n` with exactly `k` inversions, modulo `10^9 + 7`. | cses 2229 | not yet | — | — |
| Permutation OrderEither the `k`-th permutation of `1..n` in lexicographic order, or the index of a given permutation. | cses 3397 | not yet | — | — |
| Permutation Prime SumsTwo permutations of `1..n` whose position-wise sums are all prime. | cses 3423 | not yet | — | — |
| Permutation RoundsRounds until repeatedly applying the permutation restores sorted order, modulo `10^9 + 7`. | cses 3398 | not yet | — | — |
| Permutation SubsequenceA longest common subsequence of two permutations, with its length. | cses 3404 | not yet | — | — |
| PermutationsConstruct a permutation of `1..n` with no two adjacent elements differing by one, or report that none exists. | cses 1070 | not yet | — | — |
| Permuted Binary StringsFind a hidden permutation `a` of `1..n` by sending bit strings `b` and receiving `b` permuted by `a`, in at most 10 questions. | cses 3228 | no — interactive | — | — |
| Pizzeria QueriesPrice updates; cheapest delivered pizza to building `k`, price `p_a + |a - k|`. | cses 2206 | not yet | — | — |
| Planets and KingdomsLabel planets by strongly connected component with labels `1..k`, `k` the number of kingdoms. | cses 1683 | not yet | — | — |
| Planets CyclesFrom each planet, the number of teleportations until a planet is revisited. | cses 1751 | not yet | — | — |
| Planets Queries IWhere you end up after `k` teleportations from planet `x`. | cses 1750 | not yet | — | — |
| Planets Queries IIFewest teleportations from planet `a` to planet `b`, or `-1`. | cses 1160 | not yet | — | — |
| PlaylistLength of the longest contiguous run of pairwise distinct songs. | cses 1141 | not yet | — | — |
| Point in PolygonFor each query point: inside, outside, or on the boundary of a simple polygon. | cses 2192 | not yet | — | — |
| Point Location TestWhether `p₃` lies left of, right of, or on the directed line from `p₁` to `p₂`. | cses 2189 | not yet | — | — |
| Police ChaseFewest streets whose closure separates crossing `1` from crossing `n`, and such a set. | cses 1695 | not yet | — | — |
| Polygon AreaTwice the area of a simple polygon. | cses 2191 | not yet | — | — |
| Polygon Lattice PointsThe number of integer points strictly inside a simple polygon and on its boundary. | cses 2193 | not yet | — | — |
| Polynomial QueriesAdd `1, 2, 3, …` to positions `a..b` in order; range sums. | cses 1736 | not yet | — | — |
| Prefix Sum QueriesPoint updates; maximum prefix sum (empty prefix allowed) of positions `a..b`. | cses 2166 | not yet | — | — |
| Prime MultiplesHow many of `1..n` are divisible by at least one of the given primes. | cses 2185 | not yet | — | — |
| Programmers and ArtistsHire `a` programmers and `b` artists maximising the total of the relevant skills. | cses 2426 | not yet | — | — |
| ProjectsMaximum total reward of a set of projects with pairwise disjoint day ranges. | cses 1140 | not yet | — | — |
| Prüfer CodeRebuild the tree whose Prüfer code is given. The code is produced by repeatedly removing the smallest-labelled leaf and recording its neighbour, so we state correctness as: the answer is a tree on `n` nodes whose code is the given one. | cses 1134 | not yet | — | — |
| Pyramid ArrayFewest adjacent swaps making the array increase and then decrease. | cses 1747 | not yet | — | — |
| Raab Game ITwo players each play cards `1..n` in some order; the higher card scores a point per round. Given `(n, a, b)`, exhibit orders producing scores `a` and `b`, or report that none exist. | cses 3399 | not yet | — | — |
| Raab Game IINumber of card games producing the given scores, modulo `10^9 + 7`. | cses 3400 | not yet | — | — |
| Range Interval QueriesNumber of positions `i ∈ [a, b]` whose value lies in `[c, d]`. | cses 3163 | not yet | — | — |
| Range Queries and CopiesA growing list of arrays: point set in array `k`, range sum in array `k`, and copying array `k`. | cses 1737 | not yet | — | — |
| Range Update QueriesAdd `u` to every position in `a..b`; report the value at position `k`. | cses 1651 | not yet | — | — |
| Range Updates and SumsRange increase, range assignment, and range sum. | cses 1735 | not yet | — | — |
| Range Xor QueriesXor of the values at positions `a..b`. | cses 1650 | not yet | — | — |
| Reachability QueriesWhether node `b` is reachable from node `a`. | cses 2143 | not yet | — | — |
| Reachable NodesFor each node of an acyclic graph, how many nodes it reaches, itself included. | cses 2138 | not yet | — | — |
| Reading BooksTwo readers each read every book; a book cannot be read by both at once and a reader reads one book at a time. Minimum time until both have finished. | cses 1631 | not yet | — | — |
| Rectangle CuttingFewest straight integer cuts turning an `a × b` rectangle into squares. The state is the multiset of current rectangles. | cses 1744 | not yet | — | — |
| Removal GameTwo players alternately take the first or last number; each maximises their own total. The first player's total under optimal play. `margin l` is the best achievable (mover's total − other's total) from list `l`, the minimax value; the first player's total then satisfies `2·s = sum + margin`. | cses 1097 | not yet | — | — |
| Removing DigitsFewest steps to reach `0` from `n`, each step subtracting one of the current number's digits. | cses 1637 | not yet | — | — |
| Removing Digits IIFewest steps to reach `0`, each step subtracting a digit occurring in the number. | cses 2174 | not yet | — | — |
| Repeating SubstringA longest substring occurring at two or more positions, or `-1`. | cses 2106 | not yet | — | — |
| RepetitionsLength of the longest substring consisting of a single repeated character. | cses 1069 | not yet | — | — |
| Replace with DifferenceRepeatedly replace two values by their absolute difference so that `0` remains. | cses 3159 | not yet | — | — |
| Required SubstringNumber of length-`n` strings over `A`–`Z` containing the pattern, modulo `10^9 + 7`. | cses 1112 | not yet | — | — |
| Restaurant CustomersMaximum number of customers present at the same time. | cses 1619 | not yet | — | — |
| Reversal SortingSort the permutation with at most `n` subarray reversals. | cses 2075 | not yet | — | — |
| Reversals and SumsReverse a subarray, or report the sum of a subarray. | cses 2074 | not yet | — | — |
| Road ConstructionAfter each new road: the number of components and the size of the largest one. | cses 1676 | not yet | — | — |
| Road ReparationMinimum total cost of a set of roads connecting all cities, or `IMPOSSIBLE`. | cses 1675 | not yet | — | — |
| Robot PathThe robot walks the given moves from the origin and stops as soon as it revisits a point it has already been at; the total distance it travels. | cses 1742 | not yet | — | — |
| Room AllocationMinimum number of hotel rooms for customers with arrival/departure days, and an allocation achieving it. Two customers may share a room iff one departs strictly before the other arrives. | cses 1164 | not yet | — | — |
| Round TripA simple cycle through at least three cities, printed with the start repeated at the end. | cses 1669 | not yet | — | — |
| Round Trip IIA directed simple cycle through at least two cities, printed with the start repeated at the end. | cses 1678 | not yet | — | — |
| SOS Bit ProblemFor each element `x`, how many elements `y` satisfy `x ||| y = x`, `x &&& y = x` and `x &&& y ≠ 0`. | cses 1654 | not yet | — | — |
| Salary QueriesSalary changes (`! k x`) and counts of employees with salary in `[a, b]` (`? a b`). | cses 1144 | not yet | — | — |
| Same Sum SubsetsTwo disjoint non-empty subsets with equal sums, given as their elements. | cses 3425 | not yet | — | — |
| School DanceA maximum set of disjoint dance pairs among the potential pairs. | cses 1696 | not yet | — | — |
| School ExcursionWhich counts of children can visit the zoo, given that friends must go together. | cses 1706 | not yet | — | — |
| Shortest Routes IShortest route lengths from city `1` to every city along one-way flights. | cses 1671 | not yet | — | — |
| Shortest Routes IIShortest route length between two cities along two-way roads, or `-1`. | cses 1672 | not yet | — | — |
| Shortest SubsequenceA shortest DNA string that is not a subsequence of the given one. | cses 1087 | not yet | — | — |
| Signal ProcessingThe convolution of the signal with the mask. | cses 2113 | not yet | — | — |
| Sliding Window AdvertisementThe largest axis-aligned rectangle fitting under the board heights of a window. | cses 3227 | not yet | — | — |
| Sliding Window CostLeast total change making all elements of a window equal. | cses 1077 | not yet | — | — |
| Sliding Window Distinct ValuesNumber of distinct values in each window. | cses 3222 | not yet | — | — |
| Sliding Window InversionsNumber of pairs in a window whose left element exceeds the right one. | cses 3223 | not yet | — | — |
| Sliding Window MedianThe middle element of each sorted window, the smaller one when the width is even. | cses 1076 | not yet | — | — |
| Sliding Window MexThe least non-negative integer missing from each window. | cses 3219 | not yet | — | — |
| Sliding Window MinimumThe minimum of each window of `k` elements; print the xor of those minima. The array is produced by the linear generator in the input. | cses 3221 | not yet | — | — |
| Sliding Window ModeThe most frequent value in each window, the smallest one if several tie. | cses 3224 | not yet | — | — |
| Sliding Window OrThe bitwise or of each window of `k` elements; print the xor of those values. The array is produced by the linear generator in the input. | cses 3405 | not yet | — | — |
| Sliding Window SumThe sum of each window of `k` elements; print the xor of those values. The array is produced by the linear generator in the input. | cses 3220 | not yet | — | — |
| Sliding Window XorThe bitwise xor of each window of `k` elements; print the xor of those values. The array is produced by the linear generator in the input. | cses 3426 | not yet | — | — |
| Sorting MethodsFewest steps to sort the permutation under four move sets: adjacent swaps, any swap, moving an element anywhere, and moving an element to the front. | cses 1162 | not yet | — | — |
| Special SubstringsSubstrings in which every character that occurs does so equally often. | cses 2186 | not yet | — | — |
| Split into Two PathsTwo directed paths covering every node exactly once between them. | cses 3358 | not yet | — | — |
| Square SubsetsNumber of subsets whose product is a perfect square, the empty subset included, modulo `10^9 + 7`. | cses 3193 | not yet | — | — |
| Stack WeightsAfter each move, which stack is certainly heavier, given only that coin weights increase with coin number. | cses 2425 | not yet | — | — |
| Stair GameMove balls from stair `k ≠ 1` down to stair `k - 1`; the player moving last wins. | cses 1099 | not yet | — | — |
| Static Range Minimum QueriesMinimum of the values at positions `a..b`. | cses 1647 | not yet | — | — |
| Static Range Sum QueriesSum of the values at positions `a..b`. | cses 1646 | not yet | — | — |
| Stick DifferenceFor each `k`, the least possible spread of stick lengths after exactly `k` cuts. | cses 3401 | not yet | — | — |
| Stick DivisionsLeast total cost of cutting one stick into the required pieces, a cut costing the length of the stick being cut. | cses 1161 | not yet | — | — |
| Stick GameFor each heap size `1..n`, whether the player to move wins when the allowed moves remove `p` sticks for `p` in the given set. | cses 1729 | not yet | — | — |
| Stick LengthsMinimum total cost of making all sticks the same length, cost being the absolute change per stick. | cses 1074 | not yet | — | — |
| String FunctionsThe Z function and the KMP prefix function of the string. | cses 2107 | not yet | — | — |
| String MatchingNumber of positions where the pattern occurs in the string. | cses 1753 | not yet | — | — |
| String ReorderThe lexicographically least rearrangement with no two equal adjacent characters, or `-1`. | cses 1743 | not yet | — | — |
| String TransformInvert the Burrows-Wheeler transform: recover the string whose transform is the input. The transform appends `#`, sorts all rotations, and reads off their last characters. | cses 1113 | not yet | — | — |
| Strongly Connected EdgesOrient every edge so that the directed graph is strongly connected. | cses 2177 | not yet | — | — |
| Subarray DivisibilityNumber of subarrays whose sum is divisible by `n`, the array length. | cses 1662 | not yet | — | — |
| Subarray SquaresSplit the array into `k` consecutive pieces minimising the sum of squared piece sums. | cses 2086 | not yet | — | — |
| Subarray Sum ConstraintsAn integer array meeting every constraint "the sum over `l..r` is `s`". | cses 3294 | not yet | — | — |
| Subarray Sum QueriesAfter each point update, the maximum subarray sum of the whole array (empty allowed). | cses 1190 | not yet | — | — |
| Subarray Sum Queries IIMaximum subarray sum (empty allowed) within positions `a..b`. | cses 3226 | not yet | — | — |
| Subarray Sums INumber of subarrays of positive integers with sum exactly `x`. | cses 1660 | not yet | — | — |
| Subarray Sums IINumber of subarrays of integers with sum exactly `x`. | cses 1661 | not yet | — | — |
| SubordinatesFor each employee, the number of employees below them in the hierarchy. | cses 1674 | not yet | — | — |
| Subsets with Fixed AverageNumber of non-empty subsets whose average equals `a`, modulo `10^9 + 7`. | cses 3302 | not yet | — | — |
| Substring DistributionFor each length `1..n`, the number of distinct substrings of that length. | cses 2110 | not yet | — | — |
| Substring Order IThe `k`-th smallest distinct substring in lexicographic order. | cses 2108 | not yet | — | — |
| Substring Order IIThe `k`-th smallest substring counting repeats, i.e. over all `(start, length)` pairs. | cses 2109 | not yet | — | — |
| Substring ReversalsRepeatedly reverse the substring from `a` to `b`. | cses 2073 | not yet | — | — |
| Subtree QueriesNode value updates; sum of values in the subtree of a node (root `1`). | cses 1137 | not yet | — | — |
| Sum of Divisors`∑_{i=1}^n σ(i)` modulo `10^9 + 7`, where `σ` sums the divisors. | cses 1082 | not yet | — | — |
| Sum of Four SquaresFour non-negative integers whose squares sum to `n`. | cses 3355 | not yet | — | — |
| Sum of Four Values4 distinct positions (1-based) whose values sum to `x`, or `IMPOSSIBLE`. | cses 1642 | not yet | — | — |
| Sum of Three Values3 distinct positions (1-based) whose values sum to `x`, or `IMPOSSIBLE`. | cses 1641 | not yet | — | — |
| Sum of Two ValuesTwo distinct positions (1-based) whose values sum to `x`, or `IMPOSSIBLE`. | cses 1640 | not yet | — | — |
| Swap GameFewest adjacent swaps turning the `3 × 3` grid into `1..9` in order. | cses 1670 | not yet | — | — |
| Swap Round SortingFewest rounds sorting the permutation, each round performing any set of disjoint swaps, together with the swaps of each round. | cses 1698 | not yet | — | — |
| System of Linear EquationsAny solution of `n` linear equations in `m` variables modulo `10^9 + 7`, or `-1`. | cses 3154 | not yet | — | — |
| Task AssignmentA least-cost perfect matching of employees to tasks, with its cost. | cses 2129 | not yet | — | — |
| Tasks and DeadlinesProcess tasks `(duration, deadline)` back to back from time 0 in some order; reward per task is `deadline - finish`. Maximum total reward. | cses 1630 | not yet | — | — |
| Teleporters PathA route from `1` to `n` using every teleporter exactly once (an Eulerian path). | cses 1693 | not yet | — | — |
| Third PermutationA permutation differing from both given permutations at every position. | cses 3422 | not yet | — | — |
| Throwing DiceNumber of sequences of dice throws (values `1..6`) summing to `n`, modulo `10^9 + 7`. | cses 1096 | not yet | — | — |
| Tournament Graph DistributionFor each `k`, the number of tournaments on `n` nodes with exactly `k` strongly connected components, modulo `10^9 + 7`. | cses 3232 | not yet | — | — |
| Tower of HanoiMove `n` disks from stack 1 to stack 3 with the fewest moves; print the moves. The game is modelled operationally: a state is three stacks (top first, disks numbered by size), a move pops from one stack and pushes on another, and is legal only if the source is non-empty and the destination is empty or has a larger disk on top. | cses 2165 | not yet | — | — |
| TowersMinimum number of towers when cubes are stacked in order, each on a strictly larger cube. Each tower is a strictly decreasing subsequence, so the answer is the fewest strictly decreasing subsequences that partition the sequence. | cses 1073 | not yet | — | — |
| Traffic LightsAfter each traffic light is added, the longest stretch of street between consecutive lights (the ends of the street count as boundaries). | cses 1163 | not yet | — | — |
| Trailing ZerosThe number of trailing zeros of `n!`. | cses 1618 | not yet | — | — |
| Transfer Speeds SumSum over all computer pairs of the slowest connection on the route between them. | cses 3111 | not yet | — | — |
| Tree Coin Collecting IShortest walk from `a` to `b` visiting at least one node holding a coin. | cses 3114 | not yet | — | — |
| Tree Coin Collecting IIShortest walk from `a` to `b` visiting every node holding a coin. | cses 3149 | not yet | — | — |
| Tree DiameterMaximum distance between two nodes. | cses 1131 | not yet | — | — |
| Tree Distances IFor each node, the maximum distance to another node. | cses 1132 | not yet | — | — |
| Tree Distances IIFor each node, the sum of its distances to all nodes. | cses 1133 | not yet | — | — |
| Tree Isomorphism IWhether two trees rooted at node 1 are isomorphic. | cses 1700 | not yet | — | — |
| Tree Isomorphism IIWhether two unrooted trees are isomorphic. | cses 1701 | not yet | — | — |
| Tree MatchingMaximum number of edges no two of which share a node. | cses 1130 | not yet | — | — |
| Tree TraversalsGiven the preorder and inorder traversals of a binary tree, print its postorder traversal. | cses 1702 | not yet | — | — |
| Triangle Number SumsFewest triangle numbers summing to `n`. | cses 3406 | not yet | — | — |
| Two Array AverageNon-empty prefixes of both arrays maximising the average of everything chosen. | cses 3361 | not yet | — | — |
| Two KnightsFor every `k = 1..n`, the number of ways to place two knights on a `k × k` board so that they do not attack each other (unordered pairs of squares). | cses 1072 | not yet | — | — |
| Two SetsSplit `1..n` into two sets of equal sum, or report that it is impossible. | cses 1092 | not yet | — | — |
| Two Sets IINumber of ways to split `1..n` into two sets of equal sum (unordered pairs of sets), modulo `10^9 + 7`. | cses 1093 | not yet | — | — |
| Two Stacks SortingAssign each input number to one of two stacks so that popping them produces `1..n` in order. | cses 2402 | not yet | — | — |
| Visible Buildings QueriesAmong buildings `a..b`, those taller than every building before them in the range. | cses 3304 | not yet | — | — |
| Visiting CitiesThe cities appearing on every cheapest route from `1` to `n`, in increasing order. | cses 1203 | not yet | — | — |
| Water Containers MovesA sequence of moves leaving `x` units in container `A`, minimising the total water moved, or `-1`. | cses 3213 | not yet | — | — |
| Water Containers QueriesWhether `x` units can be measured in container `A`. | cses 3214 | not yet | — | — |
| Weird AlgorithmSimulate the Collatz process from `n` until it reaches `1`, printing every value. | cses 1068 | not yet | — | — |
| Word CombinationsNumber of ways to write the string as a concatenation of dictionary words, modulo `10^9 + 7`. | cses 1731 | not yet | — | — |
| Writing NumbersThe last number writable when each digit key may be pressed at most `n` times. | cses 1086 | not yet | — | — |
| Xor Pyramid DiagonalThe leftmost number of each row, from the bottom row upwards. | cses 3194 | not yet | — | — |
| Xor Pyramid PeakEach number is the xor of the two below it; find the top of the pyramid. | cses 2419 | not yet | — | — |
| Xor Pyramid RowThe `k`-th row counted from the top, which has `k` numbers. | cses 3195 | not yet | — | — |