BFS-修改范例-状态压缩

/*
BFS：二进制状态压缩
*/

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <malloc.h>
#include <ctype.h>
#include <math.h>
#include <string>
#include <iostream>
#include <algorithm>
using namespace std;
#define MAXN 11111
#include<queue>
const int INF = 999999;
struct node
{
    int x,y,step;
    int key;
};
queue<node> q;
int n,m,time;
char mp[105][105];
bool vis[105][105][20];
int xx[4]={1,-1,0,0};
int yy[4]={0,0,1,-1};
int bfs(int x,int y)
{
    node from,next;
    from.x=x,from.y=y,from.key=0,from.step=0;
    vis[x][y][0]=1;
    q.push (from);
    while(!q.empty ())
    {
        from=q.front ();
        q.pop ();
        for(int i=0;i<4;i++)
        {
            int dx=from.x+xx[i];
            int dy=from.y+yy[i];
            if(dx>=0&&dx<n&&dy>=0&&dy<m&&vis[dx][dy][from.key]==0&&mp[dx][dy]!='#')
            {
                    next.x=dx,next.y=dy,next.step=from.step+1;                                    
                if(mp[dx][dy]=='X')                
                    return from.step+1;
                else if(mp[dx][dy]>='a'&&mp[dx][dy]<='d')//find the key                 
                {
                    next.key=from.key|(1<<(mp[dx][dy]-'a'));                
                    vis[dx][dy][from.key]=1;
                    q.push (next);
                }
                else if(mp[dx][dy]>='A'&&mp[dx][dy]<='D')//find the door
                {
                    if(from.key&(1<<(mp[dx][dy]-'A')))
                    {
                        next.key=from.key;
                        vis[dx][dy][from.key]=1;
                        q.push (next);
                    }                    
                }
                else     
                {
                    vis[dx][dy][from.key]=1;                
                    next.key=from.key;
                    q.push (next);
                }
            }
        }
    }
    return -1;
}

int main()
{
    int i,j;
    int x,y;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&&m==0) break;
        memset(mp,0,sizeof(mp));
        memset(vis,0,sizeof(vis));
        while(!q.empty ())
            q.pop ();
        for(i=0;i<n;i++)
        {            
            scanf("%s",mp[i]);
            for(j=0;j<m;j++)  
            {
                if(mp[i][j]=='*')
                    x=i,y=j;                                            
                if(mp[i][j]=='B')
                    mp[i][j]='A';
                if(mp[i][j]=='Y')
                    mp[i][j]='B';
                if(mp[i][j]=='R')
                    mp[i][j]='C';
                if(mp[i][j]=='G')
                    mp[i][j]='D';

                if(mp[i][j]=='b')
                    mp[i][j]='a';
                if(mp[i][j]=='y')
                    mp[i][j]='b';
                if(mp[i][j]=='r')
                    mp[i][j]='c';
                if(mp[i][j]=='g')
                    mp[i][j]='d';
            }
        }        
        int ans=bfs(x,y);
        if(ans==-1)
            printf("The poor student is trapped!\n");
            
        else
            printf("Escape possible in %d steps.\n",ans);            
            
            
    }
    return 0;
}