记录编号	240899	评测结果	AAAAAAAAAA
题目名称	雕塑安置	最终得分	100
用户昵称	Fmuckss	是否通过	通过
代码语言	C++	运行时间	0.745 s
提交时间	2016-03-24 08:08:33	内存使用	171.15 MiB

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
long long f[21][1<<20];
int cant[21];
int settle[21];
int top;
int n, m;
long long ans; 
inline void make_settle() {
	for(int i = 1; i <= n; i++) {
		settle[i] = 1<<(i-1);
		top += settle[i];
	}
}
inline void read() {
	scanf("%d %d", &n, &m);
	int x, y;
	for(int i = 1; i <= m; i++) {
		scanf("%d %d", &x, &y);
		cant[x] += 1<<(y-1);
	}
} 
inline void solve() {
	f[0][0] = 1;
	for(int i = 1; i <= n; i++) {
		for(int j = 0; j <= top; j++) {
			if(!f[i-1][j]) continue;
			for(int k = 1; k <= n; k++) {
				if((j & settle[k]) | (cant[i] & settle[k])) continue;
				f[i][j | settle[k]] += f[i-1][j];
			} 
		}
	}
	for(int i = 0; i <= top; i++) {
		ans += f[n][i];
	}
	printf("%lld", ans);
}
int main() {
	freopen("arrange.in", "r", stdin);
	freopen("arrange.out", "w", stdout);
	read();
	make_settle();
//	if(n <= 5) {
//		dfs(1, 0);
//		printf("%lld\n", ans);
//		return 0;
//	}
	solve();
	return 0;
}