摘要：
Given a non-empty 2D array grid of 0's and 1's, an island is a group of 1's (representing land) connected 4-directionally (horizontal or vertical.) Yo 阅读全文
摘要：
Implement atoi which converts a string to an integer. The function first discards as many whitespace characters as necessary until the first non-white 阅读全文
摘要：
Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree [1,2,2,3,4,4,3] is symmet 阅读全文
摘要：
Given a sorted array, two integers k and x, find the k closest elements to x in the array. The result should also be sorted in ascending order. If the 阅读全文
摘要：
Given a non-empty list of words, return the k most frequent elements. Your answer should be sorted by frequency from highest to lowest. If two words h 阅读全文
摘要：
Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left to right, then right to left for the next level and 阅读全文
摘要：
Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or 阅读全文
摘要：
Given two words (beginWord and endWord), and a dictionary's word list, find the length of shortest transformation sequence from beginWord to endWord, 阅读全文
摘要：
Given two strings s and t, determine if they are both one edit distance apart. Note: There are 3 possiblities to satisify one edit distance apart: Exa 阅读全文
摘要：
Given a binary tree, flatten it to a linked list in-place. For example, given the following tree: The flattened tree should look like: 题目 将左子树所形成的链表插入 阅读全文
摘要：
Given an array nums of n integers and an integer target, are there elements a, b, c, and d in nums such that a + b + c + d = target? Find all unique q 阅读全文
摘要：
Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all mee 阅读全文
摘要：
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 floati 阅读全文
摘要：
Design a data structure that supports all following operations in average O(1) time. Note: Duplicate elements are allowed. Example: Solution1： HashMap 阅读全文
摘要：
Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2. Note: 题目 如题 思路 1. while loop will run as long as 阅读全文
摘要：
The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all 阅读全文