BZOJ 1079 着色方案 记忆化搜索 DP

版权声明： https://blog.csdn.net/nwpu2017300135/article/details/81665686

https://www.lydsy.com/JudgeOnline/problem.php?id=1079

题意：中文

题解：开一个六维数组，ai表示能使用i次的颜色数目，last 表示上一次用的颜色当时能用几次。

代码：

#include <iostream>
#include<cstdio>
#include<cstring>

using namespace std;
typedef long long ll;
const ll mod= 1e9+7;
ll dp[16][16][16][16][16][6];
int cnt[6];
ll dfs(int a1,int a2,int a3,int a4,int a5,int last){
	if(a1+a2+a3+a4+a5==0)return 1;
	if(dp[a1][a2][a3][a4][a5][last]!=-1)return dp[a1][a2][a3][a4][a5][last];
	ll res=0;
	if(a1>0){
		res+=(a1-(last==2))*dfs(a1-1,a2,a3,a4,a5,1);
		res%=mod;
	}
	if(a2>0){
		res+=(a2-(last==3))*dfs(a1+1,a2-1,a3,a4,a5,2);
		res%=mod;
	}
	if(a3>0){
		res+=(a3-(last==4))*dfs(a1,a2+1,a3-1,a4,a5,3);
		res%=mod;
	}
	if(a4>0){
		res+=(a4-(last==5))*dfs(a1,a2,a3+1,a4-1,a5,4);
		res%=mod;
	}
	if(a5>0){
		res+=a5*dfs(a1,a2,a3,a4+1,a5-1,5);
		res%=mod;
	}
	return dp[a1][a2][a3][a4][a5][last]=res;
}
int main()
{
	int t,i;
	int k;
	scanf("%d",&k);
	for(i=1;i<=k;i++){
		scanf("%d",&t);
		cnt[t]++;
	}
	memset(dp,-1,sizeof(dp));
	ll ans=dfs(cnt[1],cnt[2],cnt[3],cnt[4],cnt[5],0);
	printf("%lld\n",ans);
    return 0;
}