Submission #1914374

---

Source Code Expand

#include <iostream>
using namespace std;
const int mod = 1000000007;
int N, M, dp[309][309][309]; bool vis[309][309][309];
int solve(int t, int terr, int half) {
	if (t == M) return (terr == N ? 1 : 0);
	if (vis[t][terr][half]) return dp[t][terr][half];
	int ret = 0;
	if (half == 0) {
		ret = (ret + 1LL * solve(t + 1, terr, half) * terr) % mod;
		if(terr < N) ret = (ret + solve(t + 1, terr, half + 1)) % mod;
	}
	else {
		ret = (ret + 1LL * solve(t + 1, terr, half) * half) % mod;
		ret = (ret + 1LL * solve(t + 1, terr + half, 0) * terr) % mod;
		if(terr + half < N) ret = (ret + 1LL * solve(t + 1, terr, half + 1)) % mod;
	}
	vis[t][terr][half] = true;
	dp[t][terr][half] = ret;
	return ret;
}
int main() {
	cin >> N >> M;
	int ret = solve(0, 1, 0);
	for (int i = 1; i < N; i++) ret = 1LL * ret * i % mod;
	cout << ret << endl;
	return 0;
}

Submission Info

Judge Result