Generating maze is amazing! This algorithm is also widely used in lots of computer games. Given a 2D array, generate a maze in it. There are several requirements of this maze: There are no circles in the maze, which means all roads in the maze lead to an dead end or to […]
Inorder Successor in BST Given a binary search tree and a node in it, find the in-order successor of that node in the BST. Note: If the given node has no in-order successor in the tree, return null. o(h) time, o(1) space. If root->val > p->val, root is a possible […]
Given a string that contains only digits 0-9 and a target value, return all possibilities to add binary operators (not unary) +, -, or * between the digits so they evaluate to the target value. Examples: “123”, 6 -> [“1+2+3”, “1*2*3”] “232”, 8 -> [“2*3+2”, “2+3*2”] “105”, 5 -> [“1*0+5″,”10-5”] […]
Given a string, find the length of the longest substring T that contains at most 2 distinct characters. For example, Given s = “eceba”, T is “ece” which its length is 3. Two pointers. i points to the head of possible string and j points to the tail of it. […]
Graph Valid Tree Given n nodes labeled from 0 to n – 1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree. For example: Given n = 5 and edges = [[0, 1], […]
Encode and Decode Strings Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings. Machine 1 (sender) has the function: string encode(vector<string> strs) { // … your code […]
Closest Binary Search Tree Value Given a non-empty binary search tree and a target value, find the value in the BST that is closest to the target. Note: Given target value is a floating point. You are guaranteed to have only one unique value in the BST that is closest […]
Basic Calculator Implement 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 and empty spaces . You may assume that the given expression is always valid. Some examples: “1 + […]
There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of words from the dictionary, wherewords are sorted lexicographically by the rules of this new language. Derive the order of letters in this language. For example, […]
3Sum Smaller Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0 <= i < j < k < n that satisfy the condition nums[i] + nums[j] + nums[k] < target. For example, given nums = [-2, 0, 1, […]
