DOG'sTJ

这里有模拟的味道...

#include<bits/stdc++.h>
using namespace std;
int n,k;
int vis[100005]; 
struct cao
{
	int now;
	int min;	
};
int bfs(int n)
{
	queue<cao> a;
	a.push({n,0});
	while(a.size())
	{
		cao nw=a.front();
        vis[nw.now]=1;
		a.pop();
		if(nw.now==k)
		{
			return nw.min; 
		}
		else if(nw.now>k && nw.now-1>=0 && !vis[nw.now-1])
		{
			a.push({nw.now-1,nw.min+1});
		}
		else
		{
			if(nw.now+1<=100000 && !vis[nw.now+1])
			{
				a.push({nw.now+1,nw.min+1});
			}
			if(nw.now*2<=100000 && !vis[nw.now*2])
			{
				a.push({nw.now*2,nw.min+1});
			}
            if(nw.now-1>=0 && !vis[nw.now-1])
            {
                a.push({nw.now-1,nw.min+1});
            }
		}
	}
} 
int main()
{
	cin>>n>>k;
	cout<<bfs(n);
	return 0;
	
}