【记忆化搜索】bzoj1079 [SCOI2008]着色方案

#include<cstring>
#include<cstdio>
using namespace std;
#define MOD 1000000007
typedef long long ll;
ll F[16][16][16][16][16][6];
ll f(int a,int b,int c,int d,int e,int pre)
{
	if(F[a][b][c][d][e][pre]!=-1) return F[a][b][c][d][e][pre];
	if((!a)&&(!b)&&(!c)&&(!d)&&(!e)) return F[a][b][c][d][e][pre]=1;
	ll res=0;
	if(a) res=(res+((ll)(a-(pre==2))*f(a-1,b,c,d,e,1))%MOD)%MOD;
	if(b) res=(res+((ll)(b-(pre==3))*f(a+1,b-1,c,d,e,2))%MOD)%MOD;
	if(c) res=(res+((ll)(c-(pre==4))*f(a,b+1,c-1,d,e,3))%MOD)%MOD;
	if(d) res=(res+((ll)(d-(pre==5))*f(a,b,c+1,d-1,e,4))%MOD)%MOD;
	if(e) res=(res+((ll)e*f(a,b,c,d+1,e-1,5))%MOD)%MOD;
	return F[a][b][c][d][e][pre]=res;
}
int n,a[16];
int main()
{
	int x;
	scanf("%d",&n);
	for(;n;--n)
	  {
	  	scanf("%d",&x);
	  	++a[x];
	  }
	memset(F,-1,sizeof(F));
	printf("%d\n",(int)f(a[1],a[2],a[3],a[4],a[5],-1));
}