Poj Cath That Cow 需要二刷 *BFS遍历问题，自己没见过

#include<iostream>
#include<string>
#include<vector>
#include<queue>
using namespace std;

const int maxn = 100001;

bool vis[maxn];


struct node {
    int time;
    int val;
    node(int v, int t) {
        time = t;
        val = v;
    }
};

int bfs(int n, int k) {
    node no(n, 0);
    queue<node>q;
    q.push(no);
    while (!q.empty()) {
        node now = q.front();
        q.pop();
        if (now.val == k)
            return now.time;
        for (int i = 0; i < 3; i++) {
            //三种状态；
            node cur(now.val, now.time + 1);
            if (i == 0) {
                //*2情况；
                cur.val *= 2;
            }
            else if (i == 1) {
                //加1情况；
                cur.val++;
            }
            else {
                cur.val--;
            }
            if (cur.val >= 0 && cur.val <= maxn && !vis[cur.val]) {
                q.push(cur);
                vis[cur.val] = true;
            }
        }
    }
}

int main() {
    int n, k;
    cin >> n >> k;
    fill(vis, vis + maxn, false);
    cout << bfs(n, k) << endl;
    return 0;
}