Submission #2125871

---

Source Code Expand

#include <bits/stdc++.h>
using namespace std;

const int N = 305;
const int mod = 1e9 + 7;

int n, m, dp[N][N][N];

void add(int &x, int y) {
    x += y; while(x >= mod) x -= mod; while(x < 0) x += mod;
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0);
    cin >> n >> m;

    dp[0][1][1] = 1;

    for (int i = 0; i < m; ++i) {
        for (int j = 1; j <= n; ++j) {
            for (int k = 1; k <= j; ++k) {
                if (!dp[i][j][k]) continue;
                add(dp[i + 1][j + 1][k], 1LL * dp[i][j][k] * (n - j) % mod);
                add(dp[i + 1][j][k], 1LL * dp[i][j][k] * (j - k) % mod);
                add(dp[i + 1][j][j], 1LL * dp[i][j][k] * k % mod);
            }
        }
    }
    
    cout << dp[m][n][n] << endl;
}

Submission Info

Judge Result