51Nod 1092 回文字符串

最开始毫无头绪，然后参照了一位dalao的博客，思路是一个正序的字符串将其逆序，然后求最长公共子序列（LCS）,emm也属于动态规划。

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std;

const int maxn = 1105;
char s1[maxn];
char s2[maxn];

int dp[maxn][maxn];

int main(){
    cin >> s1;
    int len = strlen(s1);
    for (int i = 0,j = len - 1; i < len; i++,j--){
        s2[i] = s1[j];
    }
    memset(dp, 0, sizeof(dp));
    for (int i = 1; i <= len; i++){
        for (int j = 1; j <= len; j++){
            if (s1[i - 1] == s2[j - 1]){
                dp[i][j] = max(dp[i - 1][j - 1] + 1, max(dp[i - 1][j], dp[i][j - 1]));
            }
            else{
                dp[i][j] = max(dp[i - 1][j - 1], max(dp[i - 1][j], dp[i][j - 1]));
            }
        }
    }
    cout << len - dp[len][len] << endl;
    return 0;
}