bzoj1306

照这别人的题解写了一遍。。。囧。。。。慢的要死。。。。

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
typedef pair<int, int>p;
p com[34];
int n,tot=1;
int nscore[20], gscore[20];
int leftt[20];
int kind[4] = { 3, 1, 0, 0 };
bool check(int a)//注意这个函数是容易写错的。。。
{
	if (((nscore[a]<gscore[a])&&nscore[a] + leftt[a] * 3>=gscore[a])||nscore[a]==gscore[a])return true;
	else
		return false;
}
int anss;
void match(int num)
{
	if (num ==tot)
	{
		 anss++;
	}
	int a = com[num].first; int b = com[num].second;
	leftt[b]--; leftt[a]--;
	if (b == n)
	{
		int t = gscore[a] - nscore[a];
		if ((t == 2 || t >= 4) || t < 0)
		{
			leftt[b]++; leftt[a]++;//这里是易忽略的。。
			return;
		}
		nscore[a] += t;
		nscore[b] += kind[t];
		if (check(a)&&check(b)) match(num + 1);
		nscore[a] -= t;
		nscore[b] -= kind[t];
	}
	else
	{
		nscore[a] += 3; 
		if (check(a))
			match(num + 1);
		nscore[a] -= 3;
		nscore[b] += 3; 
		if (check(a))
		 match(num + 1); 
		nscore[b] -= 3;
		nscore[a] += 1; nscore[b] += 1;
		if (check(a))
		 match(num + 1); 
		nscore[a]--; nscore[b]--;
	}
	leftt[b]++; leftt[a]++;
	
}
int main()
{
	scanf("%d", &n);
	for (int i = 1; i <= n; i++)
		for (int j = i + 1; j <= n; j++)
			com[tot].first = i, com[tot++].second = j;
	for (int i = 1; i <= n; i++)
		scanf("%d", &gscore[i]);
	for (int i = 1; i <= n; i++)leftt[i] = n - 1;
      match(1);
	printf("%d\n", anss);
	return 0;
}