Submission #5790190

---

Source Code Expand

#include <iostream>
#include <vector>

using namespace std;

typedef long long ll;

const ll MOD = 1000000007;

int main() {
    int N, M;
    cin >> N >> M;

    vector<vector<vector<ll>>> dp(M+1, vector<vector<ll>>(N+1, vector<ll>(N+1, 0)));
    dp[0][N-1][1] = 1;
    for(int m=0;m<M;++m) {
        for(int x=0;x<N;++x) {
            for(int y=1;y<=N-x;++y) {
                if(!dp[m][x][y]) continue;
                if(x) (dp[m+1][x-1][y] += (dp[m][x][y] * x) % MOD) %= MOD;
                (dp[m+1][x][y] += (dp[m][x][y] * (N-x-y)) % MOD) %= MOD;
                (dp[m+1][x][N-x] += (dp[m][x][y] * y) % MOD) %= MOD;
            }
        }
    }

    cout << dp[M][0][N] << endl;
}

Submission Info

Judge Result