[BOJ] 1697. 숨바꼭질

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.Queue;
import java.util.Scanner;

public class Main {
	static int N,K;
	static int ans = -1;
	static boolean check[];
	static int MAX;
	static ArrayList<Integer> list = new ArrayList<Integer>();
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
        ans = -1;
        N = sc.nextInt();
        K = sc.nextInt();
        MAX = 100000;
        check = new boolean[2*MAX+1];
        bfs(N);
        System.out.println(ans);
	}
	
	public static void bfs(int N) {
		Queue<Integer> q = new LinkedList<Integer>();
		q.add(N);		
		while(!q.isEmpty()) {
			int qSize = q.size();
			for (int i = 0; i < qSize; i++) {
				int v= q.poll();
				if(v == K) {
					q.clear();
					break;
				}
				if((v-1 >= 0 && v-1 < MAX+1)&&!check[v-1]) {
					check[v-1]=true;
					q.add(v-1);
				}
				if((v+1 >= 0 && v+1 < MAX+1)&&!check[v+1]) {
					check[v+1]=true;
					q.add(v+1);
				}
				if((2*v >= 0 && 2*v < MAX+1)&&!check[2*v]) {
					check[2*v]=true;
					q.add(2*v);				
				}
			}
			ans++;
		}		
	}
}