Hdu3681Prison Break状压Dp

 

#include <cstdio>

#include <cstring>

#include <cmath>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>

using namespace std;

int dx[]={0,0,-1,1};

int dy[]={-1,1,0,0};

int vis[44][44];int dis[44][44];int Hash[1111];int Map[44][44];char str[44][44];

int len;int n,m;int Begin;

int state[1000];

const int INF=0xfffffff;

int dp[1<<17][17];

int Fin;

int Ma(int a,int b)

{

    return a>b?a:b;

}

void bfs(int x,int y)

{

    queue<int > q;

    q.push(x*m+y);

    memset(dis,0,sizeof(dis));

    memset(vis,0,sizeof(vis));

    vis[x][y]=1;dis[x][y]=0;

    while(!q.empty()){

        int cur=q.front();q.pop();

        int xx= cur/m;int yy=cur%m;

        if(~Hash[cur]){

            Map[Hash[x*m+y]][Hash[cur]]= Map[Hash[cur]][Hash[x*m+y]]=dis[xx][yy];

        }

        for(int i=0;i<4;i++){

            int x1=xx+dx[i];int y1=yy+dy[i];

            if(x1>=0&&x1<n&&y1>=0&&y1<m&&!vis[x1][y1]&&str[x1][y1]!='D'){

                vis[x1][y1]=1; dis[x1][y1]=dis[xx][yy]+1;

                q.push(x1*m+y1);

            }

        }

    }

}// 建图



int gao(int mid)

{

    memset(dp,-1,sizeof(dp));

    dp[1<<Begin][Begin] = mid;

    int gg=(1<<len);

    for(int i=0;i<gg;i++){

        for(int j=0;j<len;j++){

            if(dp[i][j]==-1) continue;

            if((i&(1<<j))==0) continue;

            if((i&Fin)==Fin){

                return 1;

            }

            for(int k=0;k<len;k++){

                if((i&(1<<k))) continue;

                if(Map[j][k]==-1||dp[i][j]<Map[j][k]) continue;

                dp[i|(1<<k)][k]=Ma(dp[i|(1<<k)][k],dp[i][j]-Map[j][k]);

                if(state[k]) dp[i|(1<<k)][k]=mid;

            }

        }

    }

    return 0;

} 





int main()

{

    while(cin>>n>>m,n||m){

        memset(state,0,sizeof(state));

        memset(Hash,-1,sizeof(Hash));

        memset(Map,-1,sizeof(Map));

        Fin = 0;len=0;

        for(int i=0;i<n;i++){

            scanf("%s",str[i]);

            for(int j=0;j<m;j++){

                if(str[i][j]=='S'||str[i][j]=='D') continue;

                Hash[i*m+j]=len;

                if(str[i][j]=='F') Begin= len,Fin|=(1<<len);

                if(str[i][j]=='G') state[len]=1;

                if(str[i][j]=='Y') Fin|=(1<<len);

                len++;

            }

        }

        for(int i=0;i<n;i++){

            for(int j=0;j<m;j++)

            if(~Hash[i*m+j]){

                bfs(i,j);

            }

        }

        int l = 0;int r=n*m+10;int gg=-1;

        while(l<=r){

            int mid= (l+r)>>1;

            if(gao(mid)){

                gg=mid;r=mid-1;

            }

            else l=mid+1;

        }

        printf("%d\n",gg);

    }

    return 0;

}