简单BFS

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <queue>
#include <map>

using namespace std;
const int N = 110;
struct Node{
    int x,y;
};
char f[N][N];
int n;

int dx[4] = {0,0,-1,1},dy[4] = {1,-1,0,0};

int bfs(Node start){
    queue<Node> Q;
    Q.push(start);
    int dist[N][N];
    memset(dist,0,sizeof dist);
    dist[start.x][start.y] = 0;


    while(!Q.empty()){
        auto t = Q.front();
        Q.pop();

        int distance = dist[t.x][t.y];
        if(f[t.x][t.y] == 'B')return distance;

        for(int i = 0;i < 4;i++){
            int nx = t.x + dx[i];
            int ny = t.y + dy[i];
            if(nx <= 0 || nx > n || ny <= 0 || ny > n)continue;
            if(f[t.x][t.y] == f[nx][ny])continue;//如果是与上面的相同则不去
            if(dist[nx][ny] == 0){
                Node news;
                news.x = nx,news.y = ny;
                dist[nx][ny] = distance + 1;
                Q.push(news);
            }
        }
    }
    return -1;
}

int main(){

    cin >> n;
    Node start;
    for(int i = 1;i <= n;i++){
        for(int j = 1;j <= n;j++){
            cin >> f[i][j];
            if(f[i][j] == 'A')start.x = i,start.y = j;
        }
    }

    cout << bfs(start) << endl;

    return 0;
}