Code Challenges

Get better at coding with practice problems.

Coding Challenges

Select a problem, write code, run test cases, and submit your solution.

Start with beginner challenges

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Guru

Implement the `criticalConnectionsBridgeCount` method that counts bridge edges in an undirected network.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Intermediate

Implement the `minimumReorderRoutesToCapital` method that returns the minimum road directions to reverse so every city can reach city zero.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `alienDictionaryOrderSize` method that returns the size of a valid alien character order.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `eventualSafeNodesCount` method that counts nodes that cannot reach a cycle.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `networkDelayTimeCost` method that returns the time needed for a signal to reach all nodes.

Array Matrix Breadth First Search

Intermediate

Implement the `closedIslandCountGrid` method that counts islands fully surrounded by water.

Array Matrix Breadth First Search

Intermediate

Implement the `enclaveLandCellCount` method that counts land cells unable to reach the boundary.

Array Matrix Breadth First Search

Proficient

Implement the `longestIncreasingPathMatrix` method that returns the longest strictly increasing path length in a matrix.

Tree Binary Tree Binary Search Tree Breadth First Search Depth First Search

Intermediate

Implement the `sumRootToLeafNumbers` method that returns the sum of all root-to-leaf numbers in a binary tree.

Tree Binary Tree Binary Search Tree Breadth First Search Depth First Search

Intermediate

Implement the `countGoodNodesBinaryTree` method that counts good nodes in a binary tree.

Tree Binary Tree Binary Search Tree Breadth First Search Depth First Search

Intermediate

Implement the `symmetricBinaryTreeCheck` method that checks whether a binary tree is a mirror of itself.

Array Matrix Breadth First Search

Guru

Implement the `maximalRectangleArea` method that returns the largest rectangle of ones in a binary matrix.

Array Matrix Breadth First Search

Proficient

Implement the `surroundedRegionsSafeCount` method that counts cells not captured in a surrounded-regions board.

Array Matrix Breadth First Search

Intermediate

Implement the `nearestZeroDistanceSum` method that returns the sum of distances from every cell to its nearest zero.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `minimumEffortPathGrid` method that returns the minimum effort required to travel across a height grid.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Intermediate

Implement the `countProvincesUnionFind` method that counts connected city groups from an adjacency matrix.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `findRedundantConnection` method that returns the edge that creates a cycle in an undirected graph.

Graph Breadth First Search Depth First Search Shortest Path Minimum Spanning Tree

Proficient

Implement the `cheapestFlightWithinKStops` method that finds the cheapest price from source to destination within a stop limit.

Array Matrix Breadth First Search

Intermediate

Implement the `matrixBlockSumCenter` method that returns the block sum around the center using distance k.