BZOJ 2595 [Wc2008]游览计划 ——斯坦纳树

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

#include <set>
#include <map>
#include <string>
#include <algorithm>
#include <vector>
#include <iostream>
#include <queue>

using namespace std;

#define maxn 11
#define F(i,j,k) for (int i=j;i<=k;++i)
#define inf (0x3f3f3f3f)

int Getint()
{
    int x=0,f=1; char ch=getchar();
    while (ch<‘0‘||ch>‘9‘) {if (ch==‘-‘) f=-1; ch=getchar();}
    while (ch>=‘0‘&&ch<=‘9‘) {x=x*10+ch-‘0‘; ch=getchar();}
    return x*f;
}

int n,m,a[maxn][maxn],cnt=0,dp[maxn][maxn][1<<maxn],pre[maxn][maxn][1<<maxn][4];
queue <int> qi,qj;
int inq[maxn][maxn],b[maxn][maxn];
int mov[4][2]={0,1,1,0,-1,0,0,-1};

void dfs(int x,int y,int k)
{
//	cout<<"dfs "<<x<<" "<<y<<" "<<k<<endl;
//	getchar();
	if (!k||!x||!y) return;
	b[x][y]=1;
	dfs(pre[x][y][k][0],pre[x][y][k][1],pre[x][y][k][2]);
	if (pre[x][y][k][2]!=k) dfs(pre[x][y][k][0],pre[x][y][k][1],k^pre[x][y][k][2]);
//	if (pre[x][y][k][0]==x&&pre[x][y][k][1]==y) dfs(pre[x][y][k][0],pre[x][y][k][1],k^pre[x][y][k][2]);
}

void out()
{
	F(i,1,n)
	{
		F(j,1,m)
			if (b[i][j])
			{
				if (a[i][j]) printf("o");
				else printf("x");
			}
			else
			{
				printf("_");
			}
		printf("\n");
	}
}

int main()
{
	memset(dp,0x3f,sizeof dp);
	n=Getint();m=Getint();
	F(i,1,n) F(j,1,m)
	{
		a[i][j]=Getint();
		if(!a[i][j])
		{
			cnt++;
			dp[i][j][1<<(cnt-1)]=0;
		}
	}
	for (int k=1;k<(1<<cnt);++k)
	{
		F(i,1,n) F(j,1,m)
		{
			for (int x=(k-1)&k;x;x=(x-1)&k)
			{
				int tmp=dp[i][j][x]+dp[i][j][k^x]-a[i][j];
				if (tmp<dp[i][j][k])
				{
					dp[i][j][k]=tmp;
					pre[i][j][k][0]=i;
					pre[i][j][k][1]=j;
					pre[i][j][k][2]=x;
				}
			}
			if (dp[i][j][k]<inf)
			{
				qi.push(i);
				qj.push(j);
				inq[i][j]=1;
			}
		}
		while (!qi.empty())
		{
			int ni=qi.front(),nj=qj.front();
			qi.pop();qj.pop();
			inq[ni][nj]=0;
			F(i,0,3)
			{
				int ti=ni+mov[i][0],tj=nj+mov[i][1];
				if (ti<=0||ti>n||tj<=0||tj>m) continue;
				if (dp[ni][nj][k]+a[ti][tj]<dp[ti][tj][k])
				{
					dp[ti][tj][k]=dp[ni][nj][k]+a[ti][tj];
					pre[ti][tj][k][0]=ni;
					pre[ti][tj][k][1]=nj;
					pre[ti][tj][k][2]=k;
					if (!inq[ti][tj])
					{
						qi.push(ti);
						qj.push(tj);
						inq[ti][tj]=1;
					}
				}
			}
		}
	}
	F(i,1,n) F(j,1,m)
	{
		if (!a[i][j])
		{
			printf("%d\n",dp[i][j][(1<<cnt)-1]);
			dfs(i,j,(1<<cnt)-1);
			out();
			return 0;
		}
	}
}