Code Challenges

Coding Challenges

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

Intermediate

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

Intermediate

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

Intermediate

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

Intermediate

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

Learner

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

Intermediate

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

Intermediate

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

Intermediate

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

Intermediate

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

Intermediate

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

Learner

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

Learner

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

Learner

Code Challenges

Get better at coding with practice problems.

Coding Challenges

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

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

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

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

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

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

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

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

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

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

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

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

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

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Practice Tests

Development Tools

Code Challenges

Get better at coding with practice problems.

Coding Challenges

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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