Submission #1799778

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Source Code Expand

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

#define for_(i,a,b) for(int i=(a);i<(b);++i)
typedef long long lint;
template< typename T > void modAdd(T& a, T b, T mod) { a = (a+b)%mod; }

int N, M;
lint dp[302][302][302];
const lint MOD = (lint)1e9 + 7;

int main() {
	cin >> N >> M;
	memset(dp, 0, sizeof(dp));
	dp[0][1][0] = 1;
	for_(i,0,M) for_(c,0,N+1) for_(s,0,N) {
		if (c+s <= N) {
			modAdd(dp[i+1][c+s][0], dp[i][c][s] * lint(c), MOD);
			modAdd(dp[i+1][c][s], dp[i][c][s] * lint(s), MOD);
		}
		if (c+s+1 <= N) modAdd(dp[i+1][c][s+1], dp[i][c][s] * lint(N-c-s), MOD);
	}
	cout << dp[M][N][0] << endl;
}

Submission Info

Judge Result