题意：

思路：

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;
const int N = 55;
char s[N];
int f[N][N];
int main(){
    scanf("%s",s + 1);
    int n = strlen(s + 1);
    memset(f,0x3f,sizeof(f));
    for(int i = 1;i <= n;i++){
        f[i][i] = 1;
    }
    for(int len = 2;len <= n;len++){
        for(int i = 1;i + len - 1 <= n;i++){
            int j = i + len - 1;
            if(s[i] == s[j]) f[i][j] = min(f[i+1][j],f[i][j-1]);
            else{
                for(int k = i;k < j;k++){
                    f[i][j] = min(f[i][j],f[i][k] + f[k+1][j]);
                }
            }
        }
    }
    printf("%d\n",f[1][n]);
    return 0;
}