Recursion

LeetCode problem #2816

Master recursive problem solving, backtracking, and exploring all solution possibilities.

Find all possible paths from source node to target node in a directed acyclic graph (DAG)

Traverse a binary tree in inorder (left -> root -> right)

Traverse a binary tree in preorder (root -> left -> right)

Traverse the boundary of a binary tree in anti-clockwise direction.

Given an array of distinct integers and a target, return all unique combinations where the chosen numbers sum to target (elements may be reused)

Construct a binary tree from preorder and inorder traversal sequences.

Convert a sorted array to a height-balanced binary search tree.

Generate the nth term of the count-and-say sequence.

Count the number of nodes in a binary tree where the path from root to that node has no nodes with values greater than the current node.

Decode a string encoded with the format k[encoded_string].

Implement depth-first search traversal for graphs

Find the diameter (longest path) of a binary tree.

Calculate the nth Fibonacci number using dynamic programming

Flatten a binary tree into a linked list in-place using preorder traversal.

Flatten a multilevel doubly linked list into a single level

Generate all possible permutations of a given string.

Invert (mirror) a binary tree by swapping left and right children

Reverse linked list in k groups (Hard): in-place pointer reversal with dummy node. Optimal O(n) time, O(1) space—step-by-step solution.

Find the lowest common ancestor of two nodes in a binary tree.

Find the maximum depth (height) of a binary tree

Find the maximum path sum in a binary tree.

Merge two sorted linked lists into one sorted linked list

Place n queens on an n x n chessboard such that no two queens attack each other, and return all distinct solutions

Check if there exists a root-to-leaf path with given sum.

Given an array of distinct integers, return all the possible permutations in any order

Traverse binary tree in postorder (left, right, root)

Print all root-to-leaf paths in a binary tree

Reverse a singly linked list in-place and return the new head.

Learn how to reverse a singly linked list (LeetCode 206) with the optimal 3-pointer iterative method: O(n) time, O(1) space. Practice now.

Given an integer array of unique elements, return all possible subsets (the power set)

Swap every two adjacent nodes in a linked list

Check if a binary tree is symmetric around its center.

Given an m x n grid of characters and a string word, return true if the word exists in the grid by traversing adjacent cells without reusing any cell