和走迷宫类似的广搜，难点在于对传送点的处理，一旦走到一个传送点，马上将坐标移动到另一个传送点

#include<bits/stdc++.h>
using namespace std;
const int N=305;
int n,m,k,s,t,a[N][N],d[N][N],dx[4]={0,0,1,-1},dy[4]={1,-1,0,0};
int ex,ey,sx,sy;
pair<int,int> h[200];//A   h['A']  h['A'+26]
char c[N][N];
queue<pair<int,int>> q;
int bfs(int sx,int sy){
	memset(d,0x3f,sizeof(d));
	d[sx][sy]=0;
	q.push({sx,sy});
	while (!q.empty()){
		int x=q.front().first;
		int y=q.front().second;
		q.pop();
		if (x==ex && y==ey) return d[x][y];
		for (int i=0;i<4;++i){
			int _x=x+dx[i];
			int _y=y+dy[i];
			char ch=c[_x][_y];
			if (_x>=1 && _x<=n && _y>=1 && _y<=m && ch!='#'){
				if (ch>='A' && ch<='Z') {
					if (h[ch]==make_pair(_x,_y)) _x=h[ch+26].first,_y=h[ch+26].second;	
					else _x=h[ch].first,_y=h[ch].second;
				}
				if (d[_x][_y]>d[x][y]+1) {
					d[_x][_y]=d[x][y]+1;
					q.push({_x,_y});
				}
			} 
		}			
	}
	return -1;
}
int main(){
//	freopen("in.txt","r",stdin);
	int x,y;
	cin>>n>>m;
	for (int i=1;i<=n;++i){
		cin>>c[i]+1;
		for (int j=1;j<=m;++j)
			if (c[i][j]=='@') sx=i,sy=j;
			else if (c[i][j]=='=') ex=i,ey=j;
			else if (c[i][j]>='A' && c[i][j]<='Z'){
				if (h[c[i][j]]==make_pair(0,0)) h[c[i][j]]={i,j};
				else h[c[i][j]+26]={i,j}; 
			}
	}
	cout<<bfs(sx,sy);
}