代码：

#include <bits/stdc++.h>
using namespace std;
struct point{
	int x,y,s;
	//bool bo;//是否有被走过(0:没走过 1:走过)
};
struct ma{
	int x1,y1,x2,y2;
}a[100];
char b[305][305];
int main(){
    int n,m;
    cin>>n>>m;
    queue<point> q;
    for(int i=1;i<=m;i++){
		for(int j=1;j<=n;j++){
			cin>>b[i][j];
			if(b[i][j]>='A' && b[i][j]<='Z'){
				if(a[b[i][j]].x1 == 0) a[b[i][j]].x1=i,a[b[i][j]].y1=j;
				else a[b[i][j]].x2=i,a[b[i][j]].y2=j;
			}
			if(b[i][j] == '@') q.push(point{i,j,0});
		}
    }
    int dx[5]={0,0,0,-1,1},dy[5]={0,-1,1,0,0};
    //BFS
    while(!q.empty()){
		point p=q.front();
		q.pop();
		
		for(int i=1;i<=4;i++){
			int xx= p.x+dx[i], yy= p.y+dy[i];
			if(xx<1 || xx>m || yy<1 || yy>n) continue;
// || p.bo==1
			if(b[xx][yy] == '#') continue;
			int step = p.s+1;
			if(b[xx][yy] == '='){
				cout<<step;
				return 0;
			} 
			if(b[xx][yy]>='A' && b[xx][yy]<='Z'){
				if(a[b[xx][yy]].x1 == xx){
					q.push( point{a[b[xx][yy]].x2, a[b[xx][yy]].y2, step} );
				}else{
					q.push( point{a[b[xx][yy]].x1, a[b[xx][yy]].y1, step} );
				}
			}
			q.push(point{xx,yy,step});
		}
    }
	return 0;
}

结果输出总是错误，0分

请大佬们帮我调一下代码