好多天没有更新了,今天有空,刷一道. 算法第5题 给定一个字符串 s,找到 s 中最长的回文子串.你可以假设 s 的最大长度为 1000. 示例 1: 输入: "babad"输出: "bab"注意: "aba" 也是一个有效答案.示例 2: 输入: "cbbd"输出: "bb" 来源:力扣(LeetCode)链接:https://leetcode-cn.com/problems/longest-palind

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Write a function to determine if a number is strobogrammatic. The number is represented as a string. For example, the numbers "69", "

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

Given an input string, reverse the string word by word. A word is defined as a sequence of non-space characters.The input string does not contain leading or trailing spaces and the words are always separated by a single space.For example,Given s = "t

A peak element is an element that is greater than its neighbors. Given an input array where num[i] ≠ num[i+1], find a peak element and return its index. The array may contain multiple peaks, in that case return the index to any one of the peaks is fi

Given an input string, reverse the string word by word. For example, Given s = "the sky is blue", return "blue is sky the". Update (2015-02-12): For C programmers: Try to solve it in-place in O(1) space. click to show clarification. Cl

Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and bl

Validate if a given string is numeric. Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => true Note: It is intended for the problem statement to be ambiguous. You

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining. For example, Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6. The above elevation map is represented by a

Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). You are given a target value to search. If found in the array return its index, otherwise return -1. You may assume no duplic

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 in non-descending order. (ie, a ≤ b ≤ c) The solut

Write a function to find the longest common prefix string amongst an array of strings. 这道题让我们求一系列字符串的共同前缀,没有什么特别的技巧,无脑查找即可,我们定义两个变量i和j,其中i是遍历搜索字符串中的字符,j是遍历字符串集中的每个字符串.这里将单词上下排好,则相当于一个各行长度有可能不相等的二维数组,我们遍历顺序和一般的横向逐行遍历不同,而是采用纵向逐列遍历,在遍历的过程中,如果某一行没有了,说明其为

Array 448.找出数组中所有消失的数 要求:整型数组取值为 1 ≤ a[i] ≤ n,n是数组大小,一些元素重复出现,找出[1,n]中没出现的数,实现时时间复杂度为O(n),并不占额外空间 思路1:(discuss)用数组下标标记未出现的数,如出现4就把a[3]的数变成负数,当查找时判断a的正负就能获取下标 tips:注意数组溢出 public List<Integer> findDisappearedNumbers(int[] nums) { List<Integer> d

又是一道有意思的题目,Count of Range Sum.(PS:leetcode 我已经做了 190 道,欢迎围观全部题解 https://github.com/hanzichi/leetcode) 题意非常简单,给一个数组,如果该数组的一个子数组,元素之和大于等于给定的一个参数值(lower),小于等于一个给定的参数值(upper),那么这为一组解,求总共有几组解. 一个非常容易想到的解法是两层 for 循环遍历子数组首尾,加起来判断,时间复杂度 O(n^2). /** * @param

题目来源 https://leetcode.com/problems/pascals-triangle/ Given numRows, generate the first numRows of Pascal's triangle. For example, given numRows = 5,Return [ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1] ] 题意分析 Input:integer Output:帕斯卡三角 Conditions:帕斯卡三

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 p

题目来源 https://leetcode.com/problems/search-in-rotated-sorted-array/ Suppose a sorted array is rotated at some pivot unknown to you beforehand. (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). You are given a target value to search. If found in the ar

题目地址:https://oj.leetcode.com/problems/two-sum/ Two Sum 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, w

================================== LeetCode的一些算法题,都是自己做的,欢迎提出改进~~ LeetCode:http://oj.leetcode.com ================================== <Reverse Words in a String>-20140328 Given an input string, reverse the string word by word. For example, Given s =

题目来源: https://leetcode.com/problems/longest-palindromic-substring/ 题意分析: 这道题目是输入一段不超过1000的字符串,输出最长的回文子字符串,输入的字符串有一个唯一的最长回文子字符串(个人觉得这个没什么用,还限制了一些输入,比如长度为2的时候肯定就只能输入两个相同的字符,还不如改为有同样长度的输出第一个最长回文子字符串,所以该题目我是按照第一个最长回文子字符串). 题目思路: 题目的字符串长度是1000,如果我们暴力解决,那么

题目来源: https://leetcode.com/problems/two-sum/ 题意分析: 这道题目是输入一个数组和target,要在一个数组中找到两个数字,其和为target,从小到大输出数组中两个数字的位置.题目中假设有且仅有一个答案. 题目思路: 如果直接暴力解决,时间复杂度为(O(n^2)),很明显这种方法会TLE. 那么如果给定的数组是有序的会不会降低难度呢?如果是有序的数组,那么我们可以用“夹逼定理”来处理.简单来说就是首尾相加,如果比target大,则将尾数左移,如果小了