POJ1159 Palindrome 【动态规划】
来源:互联网 发布:梦幻群侠传3优化版攻略 编辑:程序博客网 时间:2024/05/01 21:49
Palindrome
Time Limit: 3000MS Memory Limit: 65536KTotal Submissions: 52571 Accepted: 18124
Description
A palindrome is a symmetrical string, that is, a string read identically from left to right as well as from right to left. You are to write a program which, given a string, determines the minimal number of characters to be inserted into the string in order to obtain a palindrome.
As an example, by inserting 2 characters, the string "Ab3bd" can be transformed into a palindrome ("dAb3bAd" or "Adb3bdA"). However, inserting fewer than 2 characters does not produce a palindrome.
As an example, by inserting 2 characters, the string "Ab3bd" can be transformed into a palindrome ("dAb3bAd" or "Adb3bdA"). However, inserting fewer than 2 characters does not produce a palindrome.
Input
Your program is to read from standard input. The first line contains one integer: the length of the input string N, 3 <= N <= 5000. The second line contains one string with length N. The string is formed from uppercase letters from 'A' to 'Z', lowercase letters from 'a' to 'z' and digits from '0' to '9'. Uppercase and lowercase letters are to be considered distinct.
Output
Your program is to write to standard output. The first line contains one integer, which is the desired minimal number.
Sample Input
5Ab3bd
Sample Output
2题意:给定一个串,求最小加入几个字符能使其变成回文串。
题解:找出原串的逆串,再求n - LCS即得结果,原理是原串和逆串构成的公共序列必定是回文的,所以,对于那些不能匹配成回文的字符只需要在它与回文串中心对称的位置加上一个同样的字符即构成回文。
#include <stdio.h>#include <string.h>#define maxn 5002char str1[maxn], str2[maxn];short dp[maxn][maxn];void getTraverse(int len){int i = 1;while(len) str2[i++] = str1[len--];str2[i] = '\0';}int max(short a, short b){return a > b ? a : b;}int LCS(int len){int i, j;memset(dp, 0, sizeof(dp));for(i = 1; i <= len; ++i){for(j = 1; j <= len; ++j)if(str1[i] == str2[j]) dp[i][j] = dp[i-1][j-1] + 1;else dp[i][j] = max(dp[i-1][j], dp[i][j-1]);}return dp[len][len];}int main(){int n, len;while(scanf("%d", &n) == 1){scanf("%s", str1 + 1);len = strlen(str1 + 1);getTraverse(len);printf("%d\n", len - LCS(len));}return 0;}
0 0
- POJ1159 Palindrome 【动态规划】
- POJ1159 Palindrome (动态规划)
- poj1159 palindrome(动态规划+滚动数组)
- Palindrome(poj1159)(动态规划)
- POJ1159 Palindrome 动态规划+滚动数组
- poj1159 动态规划
- Poj1159 Palindrome(动态规划DP求最大公共子序列LCS)
- 北大POJ1159 Palindrome(动态规划求最长公共子序列)
- Palindrome(补全回文串+最长公共子序列的应用)hdu1513+poj1159+动态规划
- POJ1159 Palindrome
- poj1159 - Palindrome
- POJ1159 Palindrome
- POJ1159--Palindrome
- POJ1159 Palindrome
- poj1159 Palindrome
- POJ1159,Palindrome
- POJ1159 Palindrome
- poj1159 Palindrome
- hdu 4912 Paths on the tree(lca+贪心)
- HDU 4309 Seikimatsu Occult Tonneru(网络流-最大流)
- NSInteger与NSString互转
- hdu 3418 Beautiful Dream数学题
- 杭电ACM 1398 Square Coins(母函数)
- POJ1159 Palindrome 【动态规划】
- 第一篇。
- jdk与jre的区别
- hdu1075 字典树
- spring mvc和spring的区别
- java学习课堂笔记2
- leetcode Gas Station
- 怎么建立win7无线热点
- 杭电1233还是畅通工程