C++ 代码

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

char m[100][100];  //地图
int vis[100][100];  //标记
int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};  //方向
int n;
struct node{  //结点信息
    int x;
    int y;
    int step;
    char ch;
} first;

int bfs(node fs){
    queue<node> q;
    q.push(fs);
    while(!q.empty()){
        node now = q.front();
        if(now.ch == 'B')return now.step;
        q.pop();
        for (int i = 0; i < 4; i ++ ){
            int nx = now.x + dx[i];
            int ny = now.y + dy[i];
            if(nx>=1 && nx<=n && ny>=1 && ny<=n && m[nx][ny]!=m[now.x][now.y] && !vis[nx][ny]){
                node next;
                next.x = nx;
                next.y = ny;
                next.step = now.step + 1;
                next.ch = m[nx][ny];
                vis[nx][ny] = 1;
                q.push(next);
            }
        }
    }
    return -1;
}

int main(){
    cin>>n;
    for(int i=1; i<=n; i++){
        for(int j=1; j<=n; j++){
            cin>>m[i][j];
            if(m[i][j] == 'A'){
                first.x = i;
                first.y = j;
                first.ch = 'A';
                first.step = 0;
            }
        }
    }
    cout<<bfs(first);
    return 0;
}