BFS

#include<iostream>
#include<cstring>
#include<queue>
using namespace std;
char map[105][105];
int b[105][105];
int m,n;
int s[4][2]={-1,0,1,0,0,-1,0,1};
struct node{
    int x,y;
    int step;
};
int cheak(int x,int y)
{
    if(x>=1&&x<=m&&y>=1&&y<=n&&b[x][y]==0&&map[x][y]!='*')
        return 1;
        return 0;
}
int BFS(int x,int y)
{
    queue<node>a;
    node now;
    now.x=x;
    now.y=y;
    now.step=0;
    a.push(now);
    while(!a.empty())
    {
        now=a.front();
        a.pop();
        if(map[now.x][now.y]=='C')
        return now.step;
        for(int i=0;i<4;i++)
        {
            int dx=now.x+s[i][0];
            int dy=now.y+s[i][1];
            if(cheak(dx,dy))
            {
                node next;
                next.x=dx;
                next.y=dy;
                b[next.x][next.y]=1;
                next.step=now.step+1;
                a.push(next);
            }
        }
    }
}
int main()
{
    int k;
    while(cin>>m>>n)
    {
        for(int i=1;i<=m;i++)
        {
            cin>>(map[i]+1);
        }
        memset(b,0,sizeof(b));
        for(int i=1;i<=m;i++)
            for(int j=1;j<=n;j++)
            {
                if(map[i][j]=='B')
                {
                    b[i][j]=1;
                    k=BFS(i,j);
                    cout<<k<<endl;
                }
            } 
    }
}