The Game(HOJ1140)----BFS

#include <stdio.h>
#include <string.h>
#include <queue>
using namespace std;

typedef struct
{
    int x,y;
    int step;
}V;

queue <V> q;
char map[100][100];
int vis[100][100];

int main()
{
    int i,j,n,m,x,y,cnt,num;
    V begin,end,tag,tag1;
    num=1;
    while(1)
    {
        scanf("%d%d",&m,&n);
        gets(map[0]);
        if (n==0 && m==0) break;
        for (i=0;i<=n+2;i++)
        {
            for (j=0;j<=m+2;j++)
            {
                map[i][j]=' ';
            }
        }
        for (i=1;i<=n;i++)
        {
            gets(map[i]);
            for (j=m;j>=0;j--)
            {
                map[i][j+1]=map[i][j];
            }
            map[i][0]=' ';
        }
        cnt=1;
        printf("Board #%d:\n",num++);
        while(1)
        {
            memset(vis,0,sizeof(vis));
            scanf("%d%d%d%d",&begin.y,&begin.x,&end.y,&end.x);
            if (begin.x==0 && begin.y==0 && end.x==0 && end.y==0) break;
            while(!q.empty())
            {
                q.pop();
            }
            begin.step=0;
            q.push(begin);
            while(!q.empty())
            {
                tag=q.front();
                if (tag.x==end.x && tag.y==end.y) break;
                q.pop();
                if (vis[tag.x][tag.y]==1) continue;
                if (map[tag.x][tag.y]=='X' && (tag.x!=begin.x || tag.y!=begin.y)) continue;
                vis[tag.x][tag.y]=1;
                x=tag.x-1;
                while(x>=0)
                {
                    tag1.x=x;
                    tag1.y=tag.y;
                    tag1.step=tag.step+1;
                    q.push(tag1);
                    if (map[tag1.x][tag1.y]=='X') break;
                    x--;
                }
                x=tag.x+1;
                while(x<n+2)
                {
                    tag1.x=x;
                    tag1.y=tag.y;
                    tag1.step=tag.step+1;
                    q.push(tag1);
                    if (map[tag1.x][tag1.y]=='X') break;
                    x++;
                }
                y=tag.y-1;
                while(y>=0)
                {
                    tag1.x=tag.x;
                    tag1.y=y;
                    tag1.step=tag.step+1;
                    q.push(tag1);
                    if (map[tag1.x][tag1.y]=='X') break;
                    y--;
                }
                y=tag.y+1;
                while(y<m+2)
                {
                    tag1.x=tag.x;
                    tag1.y=y;
                    tag1.step=tag.step+1;
                    q.push(tag1);
                    if (map[tag1.x][tag1.y]=='X') break;
                    y++;
                }
            }
            if (!q.empty()) printf("Pair %d: %d segments.\n",cnt++,tag.step);
            else printf("Pair %d: impossible.\n",cnt++);
        }
        printf("\n");
    }
    return 0;
}