Graphs and traversal

BFS, DFS, shortest paths, and trees

Under construction

Still being built. Things may change

Total results6,462 problems

A graph that times out coloring backtrackingEasy1
Graph, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Friend countsEasy1
Graph, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Hands are faster than computersEasy1
Implementation, GraphNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Is Dinic quartic?Easy1
Graph, Implementation +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Find the VerticesEasy1
Graph, ImplementationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
VirusEasy2
Graph, BFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
K-Graph OddityEasy2
Graph, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
UnfriendEasy2
Tree, Brute force +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Making test data 8Easy2
Graph, Implementation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Huffman TreeEasy2
Tree, String +1No attempts yetTime limit3sMemory limit128 MB
Judgeable
The Friend of My Enemy Is My EnemyEasy2
Graph, SortingNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Sanggeun's travelsEasy2
GraphNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Toroidal gridEasy2
Implementation, GraphNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Counting FriendsEasy2
Graph, ArrayNo attempts yetTime limit1sMemory limit256 MB
Judgeable
ICPC CalculatorEasy2
Recursion, Tree +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
ITAI VirusEasy2
Graph, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Graph Maximum MatchingEasy2
Graph, Backtracking +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
László BabaiEasy2
Graph, Brute force +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Kitten on a TreeEasy2
Tree, ImplementationNo attempts yetTime limit1sMemory limit1024 MB
Judgeable
Harvest WaterlooEasy2
Graph, BFSNo attempts yetTime limit1sMemory limit1024 MB
Judgeable
LiesEasy3
Union-find, Graph +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
FriendsEasy3
Graph, Matrix +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Leaf Nodes in a TreeEasy3
Tree, DFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Come Back HomeEasy3
Backtracking, DFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
DFS and BFSEasy3
DFS, BFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Six Degrees of Kevin BaconEasy3
BFS, Graph +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Hide and SeekEasy3
BFS, GraphNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Disjoint Set OperationsEasy3
Union-findNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Avoiding Food WasteEasy3
BFS, DFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Painted AreasEasy3
BFS, DFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Travel PlanEasy3
Union-find, Graph +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Tree TraversalEasy3
Tree, DFS +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Maze SearchEasy3
BFS, Graph +1No attempts yetTime limit1sMemory limit192 MB
Judgeable
Kinship DistanceEasy3
Graph, BFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Chairperson CandidatesEasy3
Graph, BFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Housing Complex NumberingEasy3
BFS, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Keypad PasswordsEasy3
Dynamic programming, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
RadioEasy3
Graph, Shortest path +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Unreachable FunctionsEasy3
Graph, BFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
GatesEasy3
Simulation, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
NetworkingEasy3
Minimum spanning tree, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Modulo SolitaireEasy3
BFS, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Choose Your Own AdventureEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
The Great SaharaEasy3
Simulation, Implementation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Number of IslandsEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Red and BlackEasy3
DFS, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Car TroubleEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Connected or Not ConnectedEasy3
Graph, DFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Mining MapsEasy3
Hash map, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Asteroid FieldEasy3
BFS, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Breed AssignmentEasy3
Graph, Backtracking +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Daisy Chains in the FieldEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Parcel DeliveryEasy3
Shortest path, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
3D Space ExplorationEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
The Leisurely StrollEasy3
Tree, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Invasion of the MilkweedEasy3
BFS, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Feeding TimeEasy3
DFS, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Wheel RotationEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Bad GrassEasy3
Graph, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Best GrassEasy3
Array, Simulation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
S-TreesEasy3
Tree, Simulation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Shipping RoutesEasy3
Graph, BFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Help the problem setterEasy3
Tree, DFS +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
SurfingEasy3
Graph, DFS +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Making shortest-path test dataEasy3
Implementation, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Graph that exceeds Dijkstra's counterEasy3
Graph, Shortest path +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Attendance CheckEasy3
Implementation, Simulation +2No attempts yetTime limit1sMemory limit1024 MB
Judgeable
Social Networking ApplicationEasy3
Union-find, Graph +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Subdivision of KingdomEasy3
Brute force, Bit manipulation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Computation of a Road Network PlanEasy3
Tree, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
The DanceEasy3
Graph, DFSNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Network InvestmentEasy3
DFS, TreeNo attempts yetTime limit1sMemory limit128 MB
Judgeable
The HareEasy3
BFS, Graph +1No attempts yetTime limit1sMemory limit512 MB
Judgeable
Rectangle ColoringEasy3
Union-find, GeometryNo attempts yetTime limit1sMemory limit128 MB
Judgeable
The SuspectsEasy3
Union-findNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Hauling materialEasy3
Shortest path, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
The Prague LinkEasy3
Shortest path, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Robot in a MazeEasy3
BFS, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
CrankEasy3
BFS, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Strahler orderEasy3
Topological sort, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Who you knowEasy3
Shortest path, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Rainforest CanopyEasy3
DFS, Graph +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Bi-coloringEasy3
BFS, GraphNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Candy FactoryEasy3
Tree, Recursion +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Knight MovesEasy3
BFS, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Elephant ShowEasy3
DFS, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Cracking Tree CodesEasy3
Simulation, Tree +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Mystery Graph ColoringEasy3
Graph, Greedy +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Complete Binary TreeEasy3
Tree, RecursionNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Asteroids!Easy3
BFS, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Color WeaknessEasy3
BFS, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Balance ScaleEasy3
Graph, DFSNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Minion WalkEasy3
BFS, Matrix +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Neighborhoods in GraphsEasy3
BFS, GraphNo attempts yetTime limit1sMemory limit256 MB
Judgeable
The Trojan HorseEasy3
DFS, Simulation +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Counting Communication GroupsEasy3
Union-find, GeometryNo attempts yetTime limit8sMemory limit256 MB
Judgeable
Corn mazeEasy3
BFS, MatrixNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Algorist ClubEasy3
Simulation, GraphNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Permutation CyclesEasy3
Graph, DFSNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Hyacinth frequency assignmentEasy3
Tree, DFS +1No attempts yetTime limit1sMemory limit256 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
A graph that times out coloring backtrackingPrint one fixed graph: a 55-vertex clique joined by a path, chosen to make a backtracking coloring solver time out.	Easy1	GraphImplementation+1	No attempts yet	1s	128 MB	Judgeable
Friend countsCount the friends of each of N students from M mutual friendship pairs and print the N totals in order.	Easy1	GraphImplementation	No attempts yet	1s	256 MB	Judgeable
Hands are faster than computersPrint a fixed 4-vertex, 5-edge graph and a fixed proper 4-coloring, with no input to read.	Easy1	ImplementationGraph	No attempts yet	2s	512 MB	Judgeable
Is Dinic quartic?Print a fixed 4-vertex, 5-edge flow network with the exact edges and capacities given in the statement.	Easy1	GraphImplementation+1	No attempts yet	2s	512 MB	Judgeable
Find the VerticesAn interactive-style task where a hidden edge between two vertices must be identified by querying the grader; input is fixed by the grader, not read.	Easy1	GraphImplementation	No attempts yet	2s	512 MB	Judgeable
VirusCount how many computers other than computer 1 lie in computer 1's connected component of a small undirected graph.	Easy2	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
K-Graph OddityCompute the maximum vertex degree in a graph and output the smallest odd integer greater than or equal to it.	Easy2	GraphImplementation+1	No attempts yet	1s	128 MB	Judgeable
UnfriendCount the subsets of nodes in a rooted tree that can be removed, where removing a node forces removal of all its descendants.	Easy2	TreeBrute force+1	No attempts yet	2s	512 MB	Judgeable
Making test data 8Print a specific fixed graph: 98 vertices, 1501 edges forming a complete bipartite graph, using the exact listed edge order.	Easy2	GraphImplementation+2	No attempts yet	1s	128 MB	Judgeable
Huffman TreeGiven Z characters and arity N, decode the stored digit string into the per-character encoding.	Easy2	TreeString+1	No attempts yet	3s	128 MB	Judgeable
The Friend of My Enemy Is My EnemyPrint the direct friends of suspect s in increasing order for each network.	Easy2	GraphSorting	No attempts yet	1s	128 MB	Judgeable
Sanggeun's travelsGiven a connected graph of N countries and M flights, find the fewest flights that visit every country.	Easy2	Graph	No attempts yet	1s	256 MB	Judgeable
Toroidal gridPrint the given snake sweep of columns 0 to n-2 plus the climb up column n-1 to list a Hamiltonian cycle of the m by n toroidal grid.	Easy2	ImplementationGraph	No attempts yet	1s	256 MB	Judgeable
Counting FriendsCount the friends of each of N students from M mutual friendship pairs and print the N totals.	Easy2	GraphArray	No attempts yet	1s	256 MB	Judgeable
ICPC CalculatorEvaluate a dot-indented prefix expression where + sums its operands and * multiplies them.	Easy2	RecursionTree+1	No attempts yet	1s	256 MB	Judgeable
ITAI VirusCount the initially infected cities plus every city directly joined to one by a single road.	Easy2	GraphImplementation	No attempts yet	1s	256 MB	Judgeable
Graph Maximum MatchingGiven a small graph, decide whether some edges can be kept so every vertex has degree exactly 1.	Easy2	GraphBacktracking+1	No attempts yet	2s	512 MB	Judgeable
László BabaiFor each of up to 100 test cases, decide whether two simple graphs on 3 vertices given by their edge lists are isomorphic.	Easy2	GraphBrute force+1	No attempts yet	1s	256 MB	Judgeable
Kitten on a TreeGiven a tree as parent lines with their child branches and the kitten's branch K, print the path from K up to the root.	Easy2	TreeImplementation	No attempts yet	1s	1024 MB	Judgeable
Harvest WaterlooGiven a grid of pumpkins and hay bales, the task sums the values of all pumpkins reachable by orthogonal moves from a start cell.	Easy2	GraphBFS	No attempts yet	1s	1024 MB	Judgeable
LiesUsing union-find on party attendees, determine which parties can be exaggerated without conflicting with people who must always hear the truth.	Easy3	Union-findGraph+1	No attempts yet	2s	128 MB	Judgeable
FriendsGiven an N x N friendship matrix (N ≤ 50), find the maximum count of people reachable within two friendship links from any single person.	Easy3	GraphMatrix+1	No attempts yet	2s	128 MB	Judgeable
Leaf Nodes in a TreeGiven a tree by parent array, delete a node and all its descendants, then count how many leaf nodes remain.	Easy3	TreeDFS+1	No attempts yet	2s	128 MB	Judgeable
Come Back HomeCount simple paths of exact length K from the bottom-left to the top-right cell of a small grid, avoiding blocked cells and revisits.	Easy3	BacktrackingDFS+1	No attempts yet	2s	128 MB	Judgeable
DFS and BFSGiven an undirected graph, output the vertex visit order for DFS then BFS starting from a given vertex, always preferring the smallest-numbered neighbor.	Easy3	DFSBFS+1	No attempts yet	2s	128 MB	Judgeable
Six Degrees of Kevin BaconGiven an unweighted friendship graph, find the vertex whose sum of shortest distances to all others is minimal, breaking ties by smallest index.	Easy3	BFSGraph+1	No attempts yet	2s	128 MB	Judgeable
Hide and SeekCompute the minimum number of moves to reach position K from N on the number line using BFS with steps +1, -1, or doubling.	Easy3	BFSGraph	No attempts yet	2s	128 MB	Judgeable
Disjoint Set OperationsImplement a union-find structure that merges sets and answers whether two elements share a set across a sequence of operations.	Easy3	Union-find	No attempts yet	2s	128 MB	Judgeable
Avoiding Food WasteGiven a grid marked with food waste cells, find the size of the largest 4-directionally connected component using BFS/DFS or union-find.	Easy3	BFSDFS+1	No attempts yet	2s	128 MB	Judgeable
Painted AreasCount connected components of 1-cells in a grid (4-directional adjacency) and output the count and the size of the largest component.	Easy3	BFSDFS+1	No attempts yet	2s	128 MB	Judgeable
Travel PlanGiven an adjacency matrix of cities, decide if consecutive cities in a given visit order all lie in the same connected component.	Easy3	Union-findGraph+1	No attempts yet	2s	128 MB	Judgeable
Tree TraversalBuild a binary tree from parent-child input and print its preorder, inorder, and postorder traversals.	Easy3	TreeDFS+1	No attempts yet	2s	128 MB	Judgeable
Maze SearchFind the minimum number of cells traversed on a grid path from top-left to bottom-right using BFS shortest path.	Easy3	BFSGraph+1	No attempts yet	1s	192 MB	Judgeable
Kinship DistanceGiven a family forest of parent-child edges, find the shortest kinship distance between two given people or output -1 if unconnected.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
Chairperson CandidatesGiven a friendship graph, compute each member's eccentricity via shortest paths and report the minimum eccentricity value with all members achieving it.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
Housing Complex NumberingGiven a binary grid, count connected groups of adjacent 1-cells and print the number of groups plus each group's size in ascending order.	Easy3	BFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Keypad PasswordsCount length-N digit sequences on a phone keypad where consecutive digits must be adjacent keys, modulo 1,234,567, for up to N=1000.	Easy3	Dynamic programmingGraph+1	No attempts yet	1s	128 MB	Judgeable
RadioGiven a start and target frequency plus up to 5 preset shortcut buttons, find the minimum presses using +1, -1, or jump to a preset to reach the target.	Easy3	GraphShortest path+1	No attempts yet	1s	128 MB	Judgeable
Unreachable FunctionsGiven a control flow graph built from three instruction types with fall-through or jump edges, count how many functions are unreachable from the first one.	Easy3	GraphBFS+1	No attempts yet	1s	128 MB	Judgeable
GatesGiven an acyclic NAND-gate circuit whose inputs are all tied to one variable x, decide whether the overall output depends on x (answer 1) or is constant (answer 0).	Easy3	SimulationGraph+1	No attempts yet	1s	128 MB	Judgeable
NetworkingGiven points and weighted candidate cable routes, compute the minimum total cable length needed to connect all points (minimum spanning tree).	Easy3	Minimum spanning treeGraph+1	No attempts yet	1s	128 MB	Judgeable
Modulo SolitaireGiven a modulus m, up to 10 affine maps, and a start s0, find the fewest moves to reach 0.	Easy3	BFSGraph	No attempts yet	1s	128 MB	Judgeable
Choose Your Own AdventureEach page is a node with two outgoing choices or a terminal ending; print the unique path from page 1 to the single HAPPY ending.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
The Great SaharaOn a fixed 54-triangle hex board, decide whether player one can move one pyramid to trap an opponent's pyramid immediately.	Easy3	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
Number of IslandsGiven a grid of land and sea cells with 8-directional adjacency, count the connected land components.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Red and BlackCount how many black tiles are reachable from a start tile in a small grid by moving up, down, left, and right.	Easy3	DFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Car TroubleGiven a directed graph of street ids with ring road 0, report streets that cannot reach 0 and streets that 0 cannot reach, preserving input order.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Connected or Not ConnectedGiven a graph with n sites and k edges, decide whether every site can reach every other.	Easy3	GraphDFS+1	No attempts yet	1s	128 MB	Judgeable
Mining MapsParse each graph block, count distinct node names, and count distinct undirected tunnels including self-loops.	Easy3	Hash mapGraph+2	No attempts yet	1s	128 MB	Judgeable
Asteroid FieldFind the minimum number of moves from the top-left cell to the bottom-right cell in a grid, avoiding asteroid cells.	Easy3	BFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Breed AssignmentCount the breed assignments for N cows under same/different constraints, or report 0 if they conflict.	Easy3	GraphBacktracking+2	No attempts yet	1s	128 MB	Judgeable
Daisy Chains in the FieldGiven an undirected graph of cows joined by ropes, list in ascending order every cow that cannot reach cow 1, or print 0 if all cows are connected to it.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Parcel DeliveryGiven a weighted undirected graph, find the minimum total edge weight along a path from barn 1 to barn N.	Easy3	Shortest pathGraph	No attempts yet	1s	128 MB	Judgeable
3D Space ExplorationCount connected groups of '*' blocks in an N x N x N grid, where blocks connect only across shared faces.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
The Leisurely StrollGiven a rooted tree of choice-nodes where leaf edges lead to pastures, find the maximum number of edges on any root-to-pasture path.	Easy3	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
Invasion of the MilkweedSpread milkweed from a start cell to all eight neighbors each week and report the week it covers the last non-boulder cell.	Easy3	BFSGraph+2	No attempts yet	1s	128 MB	Judgeable
Feeding TimeGiven a W by H grid of grass and rock, find the size of the largest connected grass region using 8-directional adjacency.	Easy3	DFSBFS+2	No attempts yet	1s	128 MB	Judgeable
Wheel RotationGiven N-1 belts that chain N pulleys from pulley 1, with each belt either straight (same direction) or crossed (reversed), find the rotation direction of pulley N.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Bad GrassCount connected components of nonzero cells in a grid, where two cells connect if they touch horizontally, vertically, or diagonally.	Easy3	GraphDFS+2	No attempts yet	1s	128 MB	Judgeable
Best GrassCount clumps of # cells in a grid, where each clump is one cell or two orthogonally adjacent cells and different clumps never touch.	Easy3	ArraySimulation+2	No attempts yet	1s	128 MB	Judgeable
S-TreesGiven an S-tree's variable ordering and terminal labels, evaluate the Boolean function for each supplied variable assignment.	Easy3	TreeSimulation+1	No attempts yet	1s	128 MB	Judgeable
Shipping RoutesGiven warehouses and bidirectional shipping legs, answer each request with the cheapest cost, which is shipment size times the minimum number of legs times 100, or report no route.	Easy3	GraphBFS+2	No attempts yet	1s	128 MB	Judgeable
Help the problem setterFor each test case, read a binary search tree on labels 1..n and print each node's frequency, computed bottom-up as 1 plus the sum of the frequencies of all its proper descendants.	Easy3	TreeDFS+2	No attempts yet	1s	128 MB	Judgeable
SurfingParse links out of HTML pages, print each link, then answer reachability queries between pages.	Easy3	GraphDFS+1	No attempts yet	1s	128 MB	Judgeable
Making shortest-path test dataPrint the prescribed shortest-path test graph: a chain with a computed number of self-loops at vertex 0, plus Q queries from V-1 to 0.	Easy3	ImplementationGraph+2	No attempts yet	1s	128 MB	Judgeable
Graph that exceeds Dijkstra's counterPrint the exact constructed directed weighted graph that makes Floyd-Warshall finish while the lazy-deletion Dijkstra times out on one query.	Easy3	GraphShortest path+1	No attempts yet	1s	128 MB	Judgeable
Attendance CheckGiven a permutation forming one cycle, find the student who responds last when the calling chain starts at student k.	Easy3	ImplementationSimulation+2	No attempts yet	1s	1024 MB	Judgeable
Social Networking ApplicationGiven a friendship graph, answer queries asking whether two users lie in the same connected component.	Easy3	Union-findGraph+2	No attempts yet	1s	128 MB	Judgeable
Subdivision of KingdomSplit n towns (n even, n <= 26) into two halves of equal size so that the number of roads crossing between the halves is minimized.	Easy3	Brute forceBit manipulation+1	No attempts yet	1s	128 MB	Judgeable
Computation of a Road Network PlanGiven the number of cities n and a target diameter d, print a specific tree: a path of length d with all remaining cities hung off its middle vertex.	Easy3	TreeImplementation+1	No attempts yet	1s	128 MB	Judgeable
The DanceFind the largest number of boy-girl pairs that can dance at once when each boy may only invite a girl he knows.	Easy3	GraphDFS	No attempts yet	1s	128 MB	Judgeable
Network InvestmentFind the tree edge whose removal maximizes the product of the two component sizes.	Easy3	DFSTree	No attempts yet	1s	128 MB	Judgeable
The HareFind the fewest knight jumps from the start cell to the burrow on a grid with blocked cells, or output NIE when unreachable.	Easy3	BFSGraph+1	No attempts yet	1s	512 MB	Judgeable
Rectangle ColoringCount the groups of overlapping rectangles where touching edges count as overlap and each group gets one color.	Easy3	Union-findGeometry	No attempts yet	1s	128 MB	Judgeable
The SuspectsCount every student connected to student 0 through shared groups, since one suspect makes each joined group suspect.	Easy3	Union-find	No attempts yet	1s	128 MB	Judgeable
Hauling materialCompute the cheapest directed route from the start to the destination for each road network.	Easy3	Shortest pathGraph	No attempts yet	1s	128 MB	Judgeable
The Prague LinkCompute the largest shortest-path distance over all pairs of posts, or report that the network is disconnected.	Easy3	Shortest pathGraph	No attempts yet	1s	128 MB	Judgeable
Robot in a MazeFind the fewest up, down, left, or right moves from S to any G in each grid maze, or report that no exit exists.	Easy3	BFSMatrix	No attempts yet	1s	128 MB	Judgeable
CrankCount the boundary rooftops that can reach the boss by moving only to equal or lower adjacent buildings.	Easy3	BFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Strahler orderGiven a river DAG, compute its Strahler order at node M by processing nodes in topological order.	Easy3	Topological sortGraph	No attempts yet	1s	128 MB	Judgeable
Who you knowFind the cheapest chain of introductions from politician 0 to politician M-1 in an undirected graph with edge weights 1 to 4, printing -1 when unreachable.	Easy3	Shortest pathGraph	No attempts yet	1s	128 MB	Judgeable
Rainforest CanopyCount the groups of 1s connected through all eight neighbours in each square binary image.	Easy3	DFSGraph+1	No attempts yet	1s	128 MB	Judgeable
Bi-coloringCount the two-colorings where every edge joins different colors, or report -1 when the graph is not bipartite.	Easy3	BFSGraph	No attempts yet	1s	128 MB	Judgeable
Candy FactoryEach parent in a heap-ordered binary tree makes as many candies as the smaller child count, and the total subtracts consumed ingredients from all made candies.	Easy3	TreeRecursion+1	No attempts yet	1s	128 MB	Judgeable
Knight MovesFind the fewest knight moves from K to X on a grid with blocked squares, or output -1 when unreachable.	Easy3	BFSMatrix	No attempts yet	1s	128 MB	Judgeable
Elephant ShowCount the yellow tiles reachable from the elephant start by moving up, down, left, or right.	Easy3	DFSMatrix	No attempts yet	1s	128 MB	Judgeable
Cracking Tree CodesGiven a tree and its leaf-stripping code with some entries erased, the program replays the encoding to recover the missing numbers.	Easy3	SimulationTree+1	No attempts yet	1s	128 MB	Judgeable
Mystery Graph ColoringColor vertices 0 to V-1 with the smallest color unused by colored neighbors, then print the color count, the colors, and the loop counter.	Easy3	GraphGreedy+1	No attempts yet	1s	128 MB	Judgeable
Complete Binary TreeReconstruct each level of a complete binary tree from its inorder visit order.	Easy3	TreeRecursion	No attempts yet	1s	128 MB	Judgeable
Asteroids!Find the shortest 6-directional path through an N by N by N grid with blocked cells, or report that no route exists.	Easy3	BFSMatrix	No attempts yet	1s	128 MB	Judgeable
Color WeaknessCount connected R, G, B regions in an N by N grid twice, once normally and once with R and G merged.	Easy3	BFSMatrix	No attempts yet	1s	128 MB	Judgeable
Balance ScaleGiven pairwise heavier-than results, count for each object how many others have no implied comparison.	Easy3	GraphDFS	No attempts yet	1s	256 MB	Judgeable
Minion WalkMark every grid cell reachable from the top-left corner, print the room as an ASCII table, and report whether the bottom-right cell is reachable.	Easy3	BFSMatrix+1	No attempts yet	1s	256 MB	Judgeable
Neighborhoods in GraphsCount the distinct vertices at distance 1 or 2 from a query vertex in an undirected graph, excluding the vertex itself.	Easy3	BFSGraph	No attempts yet	1s	256 MB	Judgeable
The Trojan HorseMark all cells visited by patrol routes on an h by w grid, then count 4-connected unvisited regions with at least s cells.	Easy3	DFSSimulation+1	No attempts yet	1s	256 MB	Judgeable
Counting Communication GroupsCount the connected groups of camps whose circular communication areas touch or overlap.	Easy3	Union-findGeometry	No attempts yet	8s	256 MB	Judgeable
Corn mazeStarting from the single entrance on the border, move through open cells in four directions and report the farthest shortest distance.	Easy3	BFSMatrix	No attempts yet	1s	256 MB	Judgeable
Algorist ClubThe program gives each unfamiliar pair in input order the lowest free of max-degree-plus-one slots and prints zeros when a pair fits nowhere.	Easy3	SimulationGraph	No attempts yet	1s	256 MB	Judgeable
Permutation CyclesCount the disjoint directed cycles in the permutation given in each test case.	Easy3	GraphDFS	No attempts yet	1s	256 MB	Judgeable
Hyacinth frequency assignmentAssign one frequency to each edge of a tree by the stated DFS rule so each node uses at most two frequencies.	Easy3	TreeDFS+1	No attempts yet	1s	256 MB	Judgeable