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

Intermediate

Implement the `shortestPathUnweightedGraph` method that returns the shortest distance between two nodes in an unweighted graph.

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

Intermediate

Implement the `detectCycleDirectedGraph` method that checks whether a directed graph contains a cycle.

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

Intermediate

Implement the `courseSchedulePossible` method that checks whether all courses can be completed from the prerequisites.

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

Intermediate

Implement the `cloneGraphNodeCount` method that returns how many nodes are present after cloning a graph.

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

Intermediate

Implement the `numberOfIslandsDfsCount` method that counts islands in a grid using depth-first search.

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

Intermediate

Implement the `balancedBinaryTreeCheck` method that checks whether a binary tree is height-balanced.

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

Learner

Implement the `serializeTreeNodeCount` method that returns the number of nodes represented during tree serialization.

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

Intermediate

Implement the `kthSmallestInBst` method that returns the kth smallest value from a binary search tree.

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

Intermediate

Implement the `pathSumExistsTree` method that checks whether any root-to-leaf path has the target sum.

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

Intermediate

Implement the `diameterOfBinaryTree` method that returns the diameter length of a binary tree.

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

Intermediate

Implement the `lowestCommonAncestorBst` method that returns the lowest common ancestor value in a binary search tree.

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

Intermediate

Implement the `validateBinarySearchTree` method that checks whether the given tree satisfies binary search tree rules.

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

Learner

Implement the `binaryTreeLevelOrderCount` method that counts values visited during level order traversal.

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

Learner

Implement the `invertBinaryTreeValues` method that returns binary tree values after inverting left and right children.

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

Learner

Implement the `maximumDepthBinaryTree` method that returns the maximum depth of a binary tree.

Two Pointers Linked List

Intermediate

Implement the `sortLinkedListValues` method that sorts linked list values and returns the sorted list.

Two Pointers Linked List

Intermediate

Implement the `reorderLinkedListValues` method that reorders linked list values in first-last alternating order.

Two Pointers Linked List

Intermediate

Implement the `intersectionLinkedListValue` method that returns the first common value between two linked lists.

Two Pointers Linked List

Intermediate

Implement the `addTwoNumbersLinkedList` method that adds two numbers represented by linked lists and returns the result list.