[AcWing 1100] 抓住那头牛

#include<bits/stdc++.h>

using namespace std;

typedef long long LL;

const int N = 2e5 + 10;

int n, m;
int d[N];

int bfs(int x)
{
    queue<int> q;
    q.push(x);
    memset(d, -1, sizeof d);
    d[x] = 0;
    while (q.size()) {
        auto t = q.front();
        q.pop();
        if (t + 1 <= m && d[t + 1] == -1) {
            d[t + 1] = d[t] + 1;
            q.push(t + 1);
        }
        if (t - 1 >= 0 && d[t - 1] == -1) {
            d[t - 1] = d[t] + 1;
            q.push(t - 1);
        }
        if (t * 2 < N && d[t * 2] == -1) {
            d[t * 2] = d[t] + 1;
            q.push(t * 2);
        }
        if (d[m] != -1)
            return d[m];
    }
    return -1;
}

void solve()
{
    cin >> n >> m;
    cout << bfs(n) << endl;
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);

    solve();

    return 0;
}