DescriptionGiven a binary tree, return the preorder traversal of its nodes’ values. For example:Given binary tree {1,#,2,3}, 1 2 / 3return [1,2,3]. The original problem is here. The o

DescriptionImplement a basic calculator to evaluate a simple expression string. The expression string may contain open ( and closing parentheses ), the plus + or minus sign -, non-negative integers an

DescriptionDetermine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled with the character ‘.’. A partially fille

DescriptionThere are N gas stations along a circular route, where the amount of gas at station i is gas[i]. You have a car with an unlimited gas tank and it costs cost[i] of gas to travel from station

DescriptionGiven a 2d grid map of ‘1’s (land) and ‘0’s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You

DescriptionGiven an input string, reverse the string word by word. For example,Given s = “the sky is blue”,return “blue is sky the”. The original problem is here. The original code is here.

DescriptionGiven a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:Given the below binary tree

DescriptionGiven a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-leaf path 1->2->3 which represents the number 123. Find

DescriptionGiven a binary tree, find its maximum depth. The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node. The original problem is here.

DescriptionGiven a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node. The original problem is here.