ithouse的专栏

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.个人理解：求给定字符串的最长回文。 我首先想到

题目：There are two sorted arrays nums1 and nums2 of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).个人理解：给你两个已经排列好顺序的数组，求这两个数组的

刚开始的时候贪图便利，用Java自带的字符串方法进行操作，结果超时了：public class Solution { public int lengthOfLongestSubstring(String s) { int inputLength = s.length(); int longestLength = 0; for (int i = 0

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, whe

public class AddTwoNumbers { public ListNode addTwoNumbers(ListNode l1, ListNode l2) { ListNode sumNumbers = new ListNode(0); // 进位 int forward = 0; // 遍历过程进行节点添加，开始的时候

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

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 constant space. You may

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 remain as it is.You

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) and (i, 0). Find two lin

题目：Write a function to find the longest common prefix string amongst an array of strings. 解释：求输入字符串数组中最长的相同前缀public class Solution { public String longestCommonPrefix(String[] strs) { int

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,b,c) must be i

题目：Reverse digits of an integer.Example1: x = 123, return 321 Example2: x = -123, return -321理解：将输入的整数反向值输出，需要注意一点就是负号和反向之后值可能会超过int最大值的情况。public class Solution { public int reverse(int x) {

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 N A P L S I I

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 from the end, the linked list be

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: Elements in a quad

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 exactly

Implement regular expression matching with support for ‘.’ and ‘*’.‘.’ Matches any single character. ‘*’ Matches zero or more of the preceding element.The matching should cover the entire input string

题目：Determine whether an integer is a palindrome. Do this without extra space. Some hints: Could negative integers be palindromes? (ie, -1)If you are thinking of converting the integer to string, note

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:Digit strin

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 case