https://www.luogu.com.cn/record/197784678

#include <bits/stdc++.h>
using namespace std;
namespace mynamespace
{
int a,b;
struct node
{
    int v,d;
};
queue<node> q;
set<int> vis;
int bfs()
{
    q.push({a,0});
    while(!q.empty())
    {
        node now=q.front();
        vis.insert(now.v);
        q.pop();
        if(now.v==b)
        {
            return now.d;
        } 
        if(!vis.count(now.v*2)) q.push({now.v*2,now.d+1});
        if(!vis.count(now.v+1)) q.push({now.v+1,now.d+1});
        if(!vis.count(now.v-1)) q.push({now.v-1,now.d+1});
    }
}
int main()
{
    cin>>a>>b;
    cout<<bfs();
    
    return 0;
}
} 
int main()
{
    return mynamespace::main();
}