题目: 有效回文串 给定一个字符串,判断其是否为一个回文串.只包含字母和数字,忽略大小写. 样例 "A man, a plan, a canal: Panama" 是一个回文. "race a car" 不是一个回文. 注意 你是否考虑过,字符串有可能是空字符串?这是面试过程中,面试官常常会问的问题. 在这个题目中,我们将空字符串判定为有效回文. 挑战 O(n) 时间复杂度,且不占用额外空间. 解题: 去除非有效字符后,整体是个回文串,两边查找,利用快速排序的思想,…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Note: For the purpose of this problem, we define empty string as valid palindrome. Example 1: Input: "A man, a plan, a canal: Panama" O…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Notice Have you consider that the string might be empty? This is a good question to ask during an interview. For the purpose of this problem…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example, "A man, a plan, a canal: Panama" is a palindrome. "race a car" is not a palindrome. Note: Have you consider that…

Given a string S, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. For example: Given "aacecaaa", return "aaacecaaa&qu…

Given a string s, you are allowed to convert it to a palindrome by adding characters in front of it. Find and return the shortest palindrome you can find by performing this transformation. Example 1: Input: "aacecaaa" Output: "aaacecaaa&quo…

题目链接:http://poj.org/problem?id=3280 思路: dp[i][j] :=第i个字符到第j个字符之间形成回文串的最小费用. dp[i][j]=min(dp[i+1][j]+cost[s[i-1]-'a'],dp[i][j-1]+cost[s[j-1]-'a']); if(s[i-1]==s[j-1]) dp[i][j]=min(dp[i+1][j-1],dp[i][j]); 注意循环顺序,我觉得这题就是这里是tricky: #include<iostream> #i…

https://vjudge.net/problem/POJ-3280 猛刷简单dp第一天第三题. 这个据说是[求字符串通过增减操作变成回文串的最小改动次数]的变体. 首先增减操作的实质是一样的,所以输入时求min. dp[i][j]表示第i个字符到第j个字符中修改成回文串的最小代价.由于回文串的特殊性,这里两层循环的遍历方式跟常见的略有不同 这算是回文串dp的一种典型题目典型方法吧. #include<iostream> #include<cstdio> #include<…

Description 给定k个长度不超过L的01串,求有多少长度为n的01串S满足: 1.该串是回文串 2.该串不存在两个不重叠的子串,在给定的k个串中. 即不存在a<=b<c<=d,S[a,b]是k个串中的一个,S[c,d]是k个串中的一个 (It does not contain two non-overlapped substrings in the given list of K binary strings.) 举个例子,若给定2(k=2)个01串:101和1001 1010…

class Solution { public: bool isPalindrome(string s) { if(s=="") return true; ) return true; //单个字符,对称 char *p,*q; p=&s[]; //p指向开头 q=&s[s.length()-]; //q指向末尾 while(p!=q){ //测试字符串里是否有字母或数字,若没有,则立刻返回 '&&*p<'A') || (*p>'Z'&…

题目链接 题意 给定一个字符串(长度\(\leq 2e5\)),将其划分成尽量少的段,使得每段内重新排列后可以成为一个回文串. 题解 分析 每段内重新排列后是一个回文串\(\rightarrow\)该段内至多只有一个字符出现过奇数次 考虑哈希到一个\(26\)位的\(01\)串,出现过奇数次的元素位置上的值为\(1\),否则为\(0\). 于是可以继续往下推:\(\rightarrow\)该段的哈希值为\(0\)或者是\(2\)的幂次. 转化 于是问题转化为:将字符串切割成尽量少的若干段,使得每…

给一个字符串 S, 你可以通过在字符串前面添加字符将其转换为回文串.找到并返回可以用这种方式转换的最短回文串.例如:给出 "aacecaaa",返回 "aaacecaaa".给出 "abcd",返回 "dcbabcd". 详见:https://leetcode.com/problems/shortest-palindrome/description/ Java实现: 暴力解法: class Solution { public…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example,"A man, a plan, a canal: Panama"is a palindrome."race a car"is not a palindrome. Note: Have you consider that the…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome. Note:Have you consider that th…

给定一个字符串,确定它是否是回文,只考虑字母数字字符和忽略大小写.例如:"A man, a plan, a canal: Panama" 是回文字符串."race a car" 不是回文字符串.注意:你有考虑过这个字符串可能是空的吗? 在面试中这是一个很好的问题.针对此题目,我们将空字符串定义为有效的回文字符串.详见:https://leetcode.com/problems/valid-palindrome/description/ Java实现: class S…

题目链接:http://codeforces.com/contest/600/problem/C C. Make Palindrome time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output A string is called palindrome if it reads the same from left to right an…

链接:点击这里 #include<iostream> #include<algorithm> #include<stdio.h> #include<cstring> using namespace std; #define maxn 1000005 #define LL long long #define ull unsigned long long ; ull p[maxn+],f[maxn],ff[maxn]; int main(){ p[]=; ;j&…

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Note: For the purpose of this problem, we define empty string as valid palindrome. Example 1: Input: "A man, a plan, a canal: Panama" O…

问题 该文章的最新版本已迁移至个人博客[比特飞],单击链接 https://www.byteflying.com/archives/3899 访问. 给定一个字符串,验证它是否是回文串,只考虑字母和数字字符,可以忽略字母的大小写. 说明:本题中,我们将空字符串定义为有效的回文串. 输入: "A man, a plan, a canal: Panama" 输出: true 输入: "race a car" 输出: false Given a string, deter…

题目: 分割回文串 给定一个字符串s,将s分割成一些子串,使每个子串都是回文串. 返回s所有可能的回文串分割方案. 样例 给出 s = "aab",返回 [ ["aa","b"], ["a","a","b"] ] 解题: 这个题目不好搞啊,需要动态规划 在这里,没有根据动态规划,也解决了,貌似是暴力解决 从下标pos开始,找到下标i使得 pos到i内是回文字符串,再从i+1开始,找到下一…

Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters. This is case sensitive, for example "Aa" is not considered a palindrome here. Note: Assume the leng…

［抄题］: 给定一个字符串s,将s分割成一些子串,使每个子串都是回文串. 返回s所有可能的回文串分割方案. 给出 s = "aab",返回 [ ["aa", "b"], ["a", "a", "b"] ] ［思维问题］: ［一句话思路］: ［输入量］:空: 正常情况:特大:特小:程序里处理到的特殊情况:异常情况(不合法不合理的输入): ［画图］: ［一刷］: 主函数中要记得新建parti…

Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. For example, given s = "aab", Return 1 since the palindrome partitioning ["aa"…

Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. For example, given s = "aab",Return [ ["aa","b"], ["a","a","…

POJ   3974 Description Andy the smart computer science student was attending an algorithms class when the professor asked the students a simple question, "Can you propose an efficient algorithm to find the length of the largest palindrome in a string…

题意:输入一个字符串,至少插入几个字符可以变成回文串(左右对称的字符串) 分析:f[x][y]代表x与y个字符间至少插入f[x][y]个字符可以变成回文串,可以利用动态规划的思想,求解 状态转化方程: f[x][y]=0  初始化 f[x][y]=f[x+1][y-1]     s[x]==s[y]时 f[x][y]=MIN ( f[x+1][y] , f[x][y-1] )+1    s[x] != s[y]时 代码展示 一开始没有将算的的数据存放到数组中,使得有些数据重复计算好多次,TLE…

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 the restriction of using extra space. You could…

Given an integer n, find the closest integer (not including itself), which is a palindrome. The 'closest' is defined as absolute difference minimized between two integers. Example 1: Input: "123" Output: "121" Note: The input n is a po…

Given a string s, partition s such that every substring of the partition is a palindrome. Return all possible palindrome partitioning of s. Example: Input: "aab" Output: [ ["aa","b"], ["a","a","b"…

Given a string s, partition s such that every substring of the partition is a palindrome. Return the minimum cuts needed for a palindrome partitioning of s. Example: Input: "aab" Output: 1 Explanation: The palindrome partitioning ["aa"…