Binary Tree Preorder Traversal Given a binary tree, return the preorder traversal of its nodes’ values. Follow up: Recursive solution is trivial, coul ...

Binary Tree Inorder Traversal Given a binary tree, return the inorder traversal of its nodes’ values. Follow up: Recursive solution is trivial, could ...

Word Search Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, ...

Unique Paths II A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down o ...

Valid Sudoku Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each row must con ...

Sudoku Solver Write a program to solve a Sudoku puzzle by filling the empty cells. A sudoku solution must satisfy all of the following rules: Each of ...

Subsets Given a set of distinct integers, nums, return all possible subsets (the power set). Note: The solution set must not contain duplicate subsets ...

Minimum Path Sum Given a m x n grid filled with non-negative numbers, find a path from top left to bottom right which minimizes the sum of all numbers ...

Sort Colors Given an array with n objects colored red, white or blue, sort them in-place so that objects of the same color are adjacent, with the colo ...

Unique Paths A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or r ...