题解

#include<bits/stdc++.h>
#include<queue>
using namespace std;
long long n,k,r;
long long a[1000005];
int main(){
	queue<int> q;
	cin>>n>>k;
	for(int i=1;i<=100000;i++){
		a[i]=-1;
	}
	a[n]=0;
	q.push(n);
	while(!q.empty()){
		r=q.front();
		q.pop();
		if(r==k){
			cout<<a[k];
			break;
		}
		if(r>=1 && a[r-1]==-1){
			a[r-1]=a[r]+1;
			q.push(r-1);
		}
		if(r<=100000 && a[r+1]==-1){
			a[r+1]=a[r]+1;
			q.push(r+1);
		}
		if(r<=100000 && a[r*2]==-1){
			a[r*2]=a[r]+1;
			q.push(r*2);
		}
	}
	return 0;
}