HDU 1513 Palindrome（最长公共子序列）

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<cmath>
#include<deque>
#include<map>
#include<queue>
#include<cstdlib>
using namespace std;
const int maxn = 5005;

int dp[2][maxn];
char str[maxn];

int main()
{
    int n;
    while(scanf("%d",&n)!=EOF)
    {
        scanf("%s",str+1);
        memset(dp,0,sizeof(dp));
        int flag = 1;
        for(int i = 1;i <= n;++i)
        {
            flag = !flag;
            for(int j = 1;j <= n;++j)
            {
                if(str[i] == str[n-j+1])
                dp[flag][j] = dp[!flag][j-1]+1;
                else dp[flag][j] = max(dp[!flag][j],dp[flag][j-1]);
            }
        }
        printf("%d\n",n-dp[flag][n]);        
    }
    return 0;
}