【模板】BFS

#include <stdio.h>  
#include <string.h>  
#include <queue>  
using namespace std;  
  
struct node  
{  
    int x,y,step;  
};  
  
char map[105][105];  
int vis[105][105];  
int to[4][2]= {1,0,-1,0,0,1,0,-1};  
int n,m,sx,sy,ex,ey,ans;  
  
int check(int x,int y)  
{  
    if(x<0 || x>=n || y<0 || y>=m)  
        return 1;  
    if(vis[x][y] || map[x][y]=='#')  
        return 1;  
    return 0;  
}  
  
void bfs()  
{  
    int i;  
    queue<node> Q;  
    node a,next;  
    a.x = sx;  
    a.y = sy;  
    a.step = 0;  
    vis[a.x][a.y]=1;  
    Q.push(a);  
    while(!Q.empty())  
    {  
        a = Q.front();  
        Q.pop();  
        if(map[a.x][a.y]=='E')  
        {  
            ans = a.step;  
            return ;  
        }  
        for(i = 0; i<4; i++)  
        {  
            next = a;  
            next.x+=to[i][0];  
            next.y+=to[i][1];  
            if(check(next.x,next.y))  
                continue;  
            next.step=a.step+1;  
            vis[next.x][next.y] = 1;  
            Q.push(next);  
        }  
    }  
    ans = -1;  
}  
  
int main()  
{  
    int t;  
    scanf("%d",&t);  
    while(t--)  
    {  
        scanf("%d%d",&n,&m);  
        int i,j;  
        for(i = 0; i<n; i++)  
            scanf("%s",map[i]);  
        for(i = 0; i<n; i++)  
        {  
            for(j = 0; j<m; j++)  
            {  
                if(map[i][j]=='S')  
                {  
                    sx = i;  
                    sy = j;  
                }  
            }  
        }  
        memset(vis,0,sizeof(vis));  
        bfs();  
        printf("%d\n",ans);  
    }  
  
    return 0;  
}