广搜做法，MLE了，看看要怎么优化

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

struct node{
    string str;
    int step;
    node(string a, int b) {
        str = a;
        step = b;
    }
};

string A, B;
queue<node> Q;

int bfs() {
    Q.push(node(A, 0));
    while(!Q.empty()) {
        node cur = Q.front();
        Q.pop();
        for(int i = 0; i < cur.str.length() - 1; i ++) {
            string s = cur.str;
            if(s[i] == '*') s[i] = 'o';
            else s[i] = '*';
            if(s[i + 1] == '*') s[i + 1] = 'o';
            else s[i + 1] = '*';
            Q.push(node(s, cur.step + 1));
            if(s == B) {
                return cur.step + 1;
            }
        }
    }
    return 0;
}

int main(){
    cin >> A >> B;
    cout << bfs();
    return 0;
}