ZUFE 问题 R: kiminonamaewa

比较难的区间dp题

#include<bits/stdc++.h>
 
using namespace std;
 
long long  dp[60][60];
int mm = 1e9 + 7;
 
int main()
{
    int T , n ;
    string s;
    cin >> T;
    while(T --)
    {
        cin >> n;
        cin >> s;
        memset(dp,0,sizeof(dp));
        for(int i = n - 1 ; i >= 0; i--)
        {
            for(int j = i ; j < n ; j ++)
            {
                dp[i][j] = (dp[i + 1][j] + dp[i][ j - 1 ] - dp[i + 1][j - 1]) % mm;
                if( s[i] == s[j])
                    //dp[i][j] += (dp[i + 1][j - 1] + 1) % mm;
                    dp[i][j] = (dp[i][j] + dp[i + 1][j - 1] + 1) % mm;
            }
        }
        dp[0][n-1] %= mm;
        cout << dp[0][n-1] << endl;
    }
    return 0;
}