CodeForces 540C Ice Cave

題目鏈接：http://codeforces.com/problemset/problem/540/C

題目大意:給你一個地圖，有x 和 . ，x踩上去會碎，.踩上去會變成x，給出起點和終點，問能不能走到終點，且終點時終點的x碎掉；

一道bfs的題目；

代碼如下：

#include<bits/stdc++.h>
using namespace std;
char mapp[510][510];
int dir[4][2]= {1,0,-1,0,0,1,0,-1};
int kx,ky,ex,ey;
int n,m;
int ok(int x,int y)
{
    if(x<1||x>n||y<1||y>m)
        return 0;
    else
        return  1;
}
struct point
{
    int x;
    int y;

};
int BFS(int ksx,int ksy)
{
    queue<point>q;
    point sta,en,now,nown;
    en.x=ex;
    en.y=ey;
    sta.x=ksx;
    sta.y=ksy;
    q.push(sta);
    while(!q.empty())
    {
        now=q.front();
        q.pop();
        for(int i=0; i<4; i++)
        {
            nown.x=now.x+dir[i][0];
            nown.y=now.y+dir[i][1];
            if(ok(nown.x,nown.y))
            {
                if(nown.x==ex&&nown.y==ey)
                {
                    if(mapp[nown.x][nown.y]=='.')
                        mapp[nown.x][nown.y]='X';
                    else
                        return 1;
                    q.push(nown);

                }
                else if(mapp[nown.x][nown.y]=='.')
                {
                    mapp[nown.x][nown.y]='X';
                    q.push(nown);
                }
            }
        }
    }
    return 0;
}
int main()
{


    cin>>n>>m;
    for(int i=1; i<=n; i++)
        scanf("%s",mapp[i]+1);

    cin>>kx>>ky>>ex>>ey;
    if(BFS(kx,ky))
        printf("YES\n");
    else
        printf("NO\n");
}