日积月累 厚积薄发

题目：Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2.For example,Given:s1 = "aabcc",s2 = "dbbca",When s3 = "aadbbcbcac", return true.When s3 = "aadbbba

题目：The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)P A H NA P L S I I GY I RAnd then read line by line: "PAHNAPLSIIG

题目：Write a function to find the longest common prefix string amongst an array of strings.解析：求字符串数组中所有数组的最长公共前缀，重点考察细节和边界条件，比如：[] ：输入字符串数组为空，要判断if (strs .size() == 0)

leetcode上有三道关于括号符（‘（’，‘）’，‘[’，‘]’，‘{’，‘}’）匹配的问题，其中第三题是第一题的拓展，分别是：（1）Valid Parentheses，判断字符串是否是合法的括号匹配字符串（2）Generate Parentheses，根据所给的整数生成所有合法的括号匹配字符串（3）Longest Valid Parentheses，根据所给的括号字符串，求其中最长的括号匹配字符子串 下面分别讨论我对这三道题的思路的做法。

题目：Reverse digits of an integer.Example1: x = 123, return 321Example2: x = -123, return -321click to show spoilers.解析：将一个整形数字倒序输出，注意判断正负。这道题在华为面试的时候遇到过，很简单。

题目：Given a linked list, remove the nth node from the end of list and return its head.For example, Given linked list: 1->2->3->4->5, and n = 2. After removing the second node fr

题目：Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.Input:D

题目：Merge k sorted linked lists and return it as one sorted list. Analyze and describe its complexity.解析：合并k个有序链表，最后返回一个总的有序链表，分析并描述其复杂度。该题的实质为归并排序，平均时间复杂度为O(NlogN)。

题目：Given a linked list, swap every two adjacent nodes and return its head.For example,Given 1->2->3->4, you should return the list as 2->1->4->3.Your algorithm should use only cons

题目：Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.If the number of nodes is not a multiple of k then left-out nodes in the end should

leetcode上有四道关于移除有序序列中重复数字的题目，其中两道为数组结构，两道为链表结构，分别为：（1）Remove Duplicates from sorted array I：移除一个有序数组中的重复数字，并且返回新数组的大小。（2）Remove Duplicates from sorted array II：移除一个有序数组中的重复数字，并且返回新数组的大小，和上道题目不同的是每

题目：Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases.Notes: It is intended for this problem to be spe

leetcode上关于数字排列组合问题有四个，分别是：（1）Next Permutation ：已知一个数组代表某个排列组合，求出比其代表的数字大的下一个排列组合，通过重组数组中的数字实现（2）Permutations：已知一组数字，求出所有可以表示出的排列组合（3）Permutations II：已知一组数字可能包含重复，求出所有可以表示出的排列组合（无重复的）（4）Permut

题目：Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the n

题目：Implement strStr().Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.解析：实现strStr()方法，给定字符串haystack和needle，

题目：Divide two integers without using multiplication, division and mod operator.解析：

题目：Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai)

题目：Implement regular expression matching with support for '.' and '*'.'.' Matches any single character.'*' Matches zero or more of the preceding element.The matching should cover th

题目：给一组数组作为水池的高度，以其中两个高度作为水池的壁，求最大的水池容量。假设左边的壁为left，右边的壁为right，则水池容量capacity= (right-left)*min(height(right),height(right))定义两个指针left和right从数组两头开始遍历：如果left的高度低于right，则将left指针右移找

题目：这道题

今天在命令行用ant跑junit时候一直出现错误java.lang.NoClassDefFoundError: org/hamcrest/SelfDescribing查了很多资料，原来要将junit的jar包拷贝到ANT_HOME/lib下。但是之后错误还是存在，看到解释是版本问题，有提出要添加hamcrest.jar包的，试过没用。

求字符串数组中所有数组的最长公共前缀，代码很简单，但是要很注重细节边界值输入要特别注意，比如：[] 输入空的字符串数组，要判断 if (strs .size() == 0) return "";[""] 字符串数组里面只有一个空字符串等情况等等。

题目：【leetcode】12 Integer to Roman（将阿拉伯数字转换成罗马数字）

题目：Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node ne

题目：编辑距离问题是

题目：A message containing letters from A-Z is being encoded to numbers using the following mapping:'A' -> 1'B' -> 2...'Z' -> 26Given an encoded message containing digits, determine the

题目：Given a string containing only digits, restore it by returning all possible valid IP address combinations.For example:Given "25525511135",return ["255.255.11.135", "255.255.111.35"]

题目：Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the lengt

Two Sum 题目：My SubmissionsGiven 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, where index1 must be less than ind

类似于中国围棋的二维字符数组，将被'X'包围的'O'全部转化为'X'，不同的是，与边缘接轨的'O'不用转化为'X'，所以切入点在于边缘的‘O’，从边缘开始做DFS或者BFS，由于用例有200*200的棋盘，使用Java写DFS会因为递归太多层报Stackoverflow的错误，用C++实现能够AC：

解析：求两个排序数组的中位数，数组长度分别是m和n，要求时间复杂度为O(log(m+n)）。刚开始思路是利用类似合并排序的思路分别遍历两个数组，但是算法复杂度为O(n)。查看网上的解题方法，原问题其实是一个寻找第k小数的问题，中位数实际上是第(m+n)/2小的数。对于数组a和b，比较A的第k/2小的元素A[k/2-1]和B的第k/2小的元素B[k/2-1]两个元素，有三种情况可以考虑：1. A[k/2-1]<B[k/2-1]表示A[0]到A[k/2-1]的元素都在A和B合并之后的前k小的元素中，可以把A

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 a linked list.Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)Outpu

题目：Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.解析：求一个字符串的最长回文子串。有三种解法，并且时间不断在优化：解法一：暴力解法，遍历字符串，将每个字符做子串中心，向两端扩展，时间复杂度O(N^2

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