Wildcard Matching Implement wildcard pattern matching with support for ‘?’ and ‘*’. ‘?’ Matches any single character. ‘*’ Matches any sequence of characters (including the empty sequence). The matching should cover the entire input string (not partial). The function prototype should be: bool isMatch(const char *s, const char *p) Some examples: isMatch(“aa”,”a”) → […]

Kth Smallest Element in a BST Given a binary search tree, write a function kthSmallest to find the kth smallest element in it. Note: You may assume k is always valid, 1 ≤ k ≤ BST’s total elements. Follow up: What if the BST is modified (insert/delete operations) often and you need to […]

Given a sorted integer array without duplicates, return the summary of its ranges. For example, given [0,1,2,4,5,7], return [“0->2″,”4->5″,”7”]. Credits: Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.     class Solution { public: vector<string> summaryRanges(vector<int>& nums) { vector<string> ans; string range; if(nums.size() == 0) […]

Sliding Window Maximum Given an array nums, there is a sliding window of size k which is moving from the very left of the array to the very right. You can only see the k numbers in the window. Each time the sliding window moves right by one position. For example, Given nums = [1,3,-1,-3,5,3,6,7], and k = 3. Window […]

The Skyline Problem A city’s skyline is the outer contour of the silhouette formed by all the buildings in that city when viewed from a distance. Now suppose you are given the locations and height of all the buildings as shown on a cityscape photo (Figure A), write a program […]

Word Search II Given a 2D board and a list of words from the dictionary, find all words in the board. Each word must be constructed from letters of sequentially adjacent cell, where “adjacent” cells are those horizontally or vertically neighboring. The same letter cell may not be used more […]

Implement Trie (Prefix Tree) Implement a trie with insert, search, and startsWith methods. Note: You may assume that all inputs are consist of lowercase letters a-z. Use TrieNode * child[26] to denote 26 possible successors. Use count to denote the number of words that end at current node. If count […]

Shortest Word Distance I Given a list of words and two words word1 and word2, return the shortest distance between these two words in the list. For example, Assume that words = [“practice”, “makes”, “perfect”, “coding”, “makes”]. Given word1 = “coding”, word2 = “practice”, return 3. Given word1 = “makes”, word2 = “coding”, return 1. Note: You may assume that word1 does not equal to word2, and word1 and word2 are both in […]

Game of Life According to the Wikipedia’s article: “The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970.” Given a board with m by n cells, each cell has an initial state live (1) or dead (0). […]

here are a row of n houses, each house can be painted with one of the three colors: red, blue or green. The cost of painting each house with a certain color is different. You have to paint all the houses such that no two adjacent houses have the same color. The […]