找字符串里最长回文串的长度（不一定连续）

#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
using namespace std;
const int N = 1010;
int f[N][N];
int main(){
    string s;
    cin>>s;
    string b(s);
    reverse(b.begin(),b.end());
    for(int i = 1;i<=s.size();i++){
        for(int j = 1;j<=s.size();j++){
            f[i][j] = max(f[i-1][j],f[i][j-1]);
            if(s[i-1] == b[j-1]) f[i][j] = max(f[i][j],f[i-1][j-1]+1);
        }
    }
    cout<<s.size()-f[s.size()][s.size()];
    return 0;
}