Submission #1352063

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Source Code Expand

#include<iostream>
#include<algorithm>
using namespace std;
long long n, m, dp[305][305][305], mod = 1000000007;
long long solve(long long pos, long long rec1, long long rec2) {
	if (rec1 + rec2 > n)return 0;
	if (pos == m) {
		if (rec1 == n && rec2 == 0)return 1;
		return 0;
	}
	if (dp[pos][rec1][rec2] >= 1)return dp[pos][rec1][rec2] - 1;
	long long ret = 0;
	ret += solve(pos + 1, rec1 + rec2, 0)*rec1;
	ret += solve(pos + 1, rec1, rec2)*rec2;
	ret += solve(pos + 1, rec1, rec2 + 1)*(n - rec1 - rec2); ret %= mod;
	dp[pos][rec1][rec2] = ret + 1;
	return ret;
}
int main() {
	cin >> n >> m;
	cout << solve(0, 1, 0) << endl;
	return 0;
}

Submission Info

Judge Result