HDU 1693 Eat the Trees

插头DP，多条回路求回路数。

可以当作模版来记。注重理解轮廓线。

#include <iostream>
#include <string.h>
#include <iostream>
#include <stdio.h>

using namespace std;

const int HASH=10007;
const int STATE=5000; //状态数
const int MAXD=15;

int code[MAXD],maze[MAXD][MAXD];
int N,M;

struct HASHMAP
{
	int head[HASH],next[STATE],state[STATE],size;
	long long f[STATE];
	void init()
	{
		size=0;
		memset(head,-1,sizeof(head));
	}
	void push(int st,long long ans)
	{
		int i,h=st%HASH;
		for(i=head[h];i!=-1;i=next[i])
			if(st==state[i])
			{
				f[i]+=ans;
				return;
			}
		f[size]=ans;
		state[size]=st;
		next[size]=head[h];
		head[h]=size++;
	}
}hm[2];

void decode(int *code,int m,int st)
{
	int i;
	for(i=m;i>=0;i--)
	{
		code[i]=st&1;
		st>>=1;
	}
}

int encode(int *code,int m)
{
	int i,st=0;
	for(i=0;i<=m;i++)
	{
		st<<=1;
		st|=code[i];
	}
	return st;
}

void init()
{
	scanf("%d%d",&N,&M);
	for(int i=1;i<=N;i++)
		for(int j=1;j<=M;j++)
			scanf("%d",&maze[i][j]);
	for(int i=1;i<=N;i++)maze[i][M+1]=0;
	for(int i=1;i<=M;i++)maze[N+1][i]=0;//边界补0
}

void shift(int *code,int m)//换行
{
	int i;
	for(i=m;i>0;i--)
		code[i]=code[i-1];
	code[0]=0;
}

void dpblank(int i,int j,int cur)
{
	int k,left,up;
	for(k=0;k<hm[cur].size;k++)
	{
		decode(code,M,hm[cur].state[k]);
		left=code[j-1];
		up=code[j];
		if(left&&up)//左边和上边都有插头
		{
			code[j-1]=code[j]=0;
			if(j==M)shift(code,M);
			hm[cur^1].push(encode(code,M),hm[cur].f[k]);
		}
		else if(left||up)
		{
			if(maze[i][j+1])
			{
				code[j-1]=0;
				code[j]=1;
				hm[cur^1].push(encode(code,M),hm[cur].f[k]);
			}
			if(maze[i+1][j])
			{
				code[j-1]=1;
				code[j]=0;
				if(j==M)shift(code,M);
				hm[cur^1].push(encode(code,M),hm[cur].f[k]);
			}
		}
		else
		{
			if(maze[i+1][j]&&maze[i][j+1])
			{
				code[j]=code[j-1]=1;
				hm[cur^1].push(encode(code,M),hm[cur].f[k]);
			}
		}
	}
}

void dpblock(int i,int j,int cur)
{
	int k;
	for(k=0;k<hm[cur].size;k++)
	{
		decode(code,M,hm[cur].state[k]);
		code[j-1]=code[j]=0;
		if(j==M)shift(code,M);
		hm[cur^1].push(encode(code,M),hm[cur].f[k]);
	}
}

void solve()
{
	int i,j,cur;
	long long ans=0;
	cur=0;
	hm[cur].init();
	hm[cur].push(0,1);
	for(i=1;i<=N;i++)
		for(j=1;j<=M;j++)
		{
			hm[cur^1].init();
			if(maze[i][j])dpblank(i,j,cur);
			else dpblock(i,j,cur);
			cur^=1;
		}
	for(i=0;i<hm[cur].size;i++)
		ans+=hm[cur].f[i];
	printf("There are %I64d ways to eat the trees.\n",ans);
}

int main()
{
	/*freopen("in.txt","r",stdin);
	freopen("out.txt","w",stdout);*/
	int T;
	int iCase=0;
	scanf("%d",&T);
	while(T--)
	{
		iCase++;
		printf("Case %d: ",iCase);
		init();
		solve();
	}
	return 0;
}

HDU 1693 Eat the Trees,布布扣,bubuko.com

HDU 1693 Eat the Trees

原文：http://blog.csdn.net/imutzcy/article/details/25708019