最小转弯次数问题与最短路的不同

#include<bits/stdc++.h>
using namespace std;
char mp[200][200];
struct ty{
    int x,y;
    int num;
    int fx;
    bool operator < (const ty&y) const{
        return num>y.num;
    }
};
int ex,ey;
int sx,sy; 
int n;
int vis[200][200][5];
int dx[5] = {0,1,0,-1,0};
int dy[5] = {0,0,1,0,-1};
priority_queue<ty> q;
int bfs(){
    q.push({sx,sy,0,0});
    while(!q.empty()){
        auto op = q.top();
        q.pop();
        int xx = op.x;
        int yy = op.y;
       // if(vis[xx][yy][op.fx]) continue;
        vis[xx][yy][op.fx] = 1;
        if(xx==ex&&yy==ey) return op.num;
        for(int i = 1;i<=4;i++){
            int nx = xx + dx[i];
            int ny = yy + dy[i];
            if(mp[nx][ny]!='x'&&!vis[nx][ny][i]&&nx>=1&&nx<=n&&ny>=1&&ny<=n){
                if(op.fx==0){
                    q.push({nx,ny,0,i});
                }
                else{
                if(op.fx==i){
                   // cout<<nx<<" "<<ny<<endl;
                   // cout<<op.num<<" !"<<endl;
                    q.push({nx,ny,op.num,i});
                }
                else{
                    q.push({nx,ny,op.num+1,i});  
                }
            }
            }
        }
        
    }
    return -1;
}
int main(){
    cin>>n;
  //  cout<<1<<endl;
    for(int i = 1;i<=n;i++){
        for(int j = 1;j<=n;j++){
           cin>>mp[i][j];
            if(mp[i][j] =='A'){
                sx = i;
                sy = j;
            }
            if(mp[i][j] =='B'){
                ex = i;
                ey = j;
            }
        }
    }
    memset(vis,0,sizeof(vis));
    cout<<bfs();
}