hwb1992

题目 Given a collection of numbers, return all possible permutations. For example, [1,2,3] have the following permutations: [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1]. 思路 这道题是个递

题目 You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as

题目 Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? 思路  通过快慢指针来做.如果存在环，那么通过快慢指针，一定可以让快指针指向满指针（并且快指针指向的当前位置和下一个位置都不是null 但是如果不存在环

题目 Given two binary strings, return their sum (also a binary string). For example, a = "11" b = "1" Return "100". 思路 恩..其实这道题可以简单点的，用BigInteger来做..比较恶心.. 但是还是乖点，用标准的做法吧 分析：      2个二进

题目 Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: Ele

题目 Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target,

题目 Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: Elements in a triplet (a,

题目 Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have e

题目 You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and with

Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted from left to right.The first integer of each

题目 Given an array of strings, return all groups of strings that are anagrams. Note: All inputs will be in lower-case. 思路 这个题目是判断所给的字符串数组中是否存在重复的颠倒字符串. 解决思路如下 首先为每个字符串排序   -->这个是用来判断是否存在重复的颠倒

题目 Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are +, -, *, /. Each operand may be an integer or another expression. Some examples: ["2", "1"

题目 Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example, [1,1,2] have the following unique permutations: [1,1,2], [1,2,1], and [2,1,1

题目 Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Follow up: Can you solve it without using extra space? 思路 本来我傻傻的用  Linked List Cycle 的方法来做，