题解 | #[SCOI2005]互不侵犯KING#

#include <bits/stdc++.h>
using namespace std;
#define ll long long
int n, k;
int num[1000];
ll f[10][90][1000];
int calc(int x)
{
	int cnt = 0;
	while (x)
	{
		if (x & 1) cnt++;
		x >>= 1;
	}
	return cnt;
}

int main()
{
	scanf("%d%d", &n, &k);
	for (int st = 0; st < (1 << n); st++)
	{
		num[st] = calc(st);
	}
	f[0][0][0] = 1;
	for (int i = 1; i <= n; i++)
	{
		for (int j = 0; j <= k; j++)
		{
			for (int st = 0; st < (1 << n); st++)
			{
				if (num[st] > j) continue;
				if (st & (st << 1))continue;
				for (int last = 0; last < (1 << n); last++)
				{
					if (last & (last << 1)) continue;
					if (last & st) continue;
					if (last & (st >> 1)) continue;
					if (last & (st << 1))continue;
					f[i][j][st] += f[i - 1][j - num[st]][last];
				}
			}
		}
	}
	int ans = 0;
	for (int st = 0; st < (1 << n); st++)
	{
		ans += f[n][k][st];
	}

	cout << ans;

	return 0;
}