题解BFS

#include <bits/stdc++.h>
using namespace std;
int n,k;
int a[100005];
int main(){

cin>>n>>k;
for(int i=1;i<=100000;i++){
	a[i]=-1;
}
a[n]=0;
queue <int> que;
que.push(n);
while(que.size()){
	int r=que.front();
	que.pop();
	if(r==k){
		cout<<a[k];
        break;
	}
	if(r>=1&&a[r-1]==-1){
		a[r-1]=a[r]+1;
		que.push(r-1);
	}
	if(r+1<=100000&&a[r+1]==-1){
		a[r+1]=a[r]+1;
		que.push(r+1);
	}
	if(2*r<=100000&&a[2*r]==-1){
		a[2*r]=a[r]+1;
		que.push(2*r);
	}
}
return 0;

}