第三个帖子了.

#include<iostream>
#include<cstdio>
#include<queue>
using namespace std;

int n,m,x1,y1,x2,y2;
char map[503][503];
int step[503][503];
bool vis[503][503];
int dx[]={1,0,-1,0};
int dy[]={0,-1,0,1};

inline void bfs(){
    deque<pair<int,int> >q;
    q.push_back(make_pair(x1,y1));
    step[x1][y1]=0;
    vis[x1][y1]=1;

    while(q.size()){
        int x=q.front().first,
            y=q.front().second;
            q.pop_front();
        for(register int i=0;i<4;++i){
            int xx=x+dx[i];
            int yy=y+dy[i];   
            if(xx<0||xx>n||yy<0||yy>m||vis[xx][yy])
                continue;
            int w=map[x][y]!=map[xx][yy];
            if(w)q.push_back(make_pair(xx,yy));
            else q.push_front(make_pair(xx,yy));
            step[xx][yy]=step[x][y]+w;
			if(xx==x2&&yy==y2)return; 
            vis[xx][yy]=1;     
        }
    }
}

int main(){
    while(1){
        scanf("%d%d",&n,&m);
        if(n==0&&m==0)break;
        for(register int i=0;i<n;++i)
            for(register int j=0;j<m;j++){
				step[i][j]=0;
				vis[i][j]=0;
                cin>>map[i][j];
			}
        scanf("%d%d%d%d",&x1,&y1,&x2,&y2);     
        if(x1==x2&&y1==y2){
            printf("0\n");
            continue;
        }
        bfs();
        printf("%d\n",step[x2][y2]);
    }
    return  0;
}