백준 1697번 파이썬 bfs

from collections import deque

def bfs():

    queue=deque()

    queue.append(n)

    while queue:

        a=queue.popleft()

        if a==k:

            print(arr[a])

            break

        for na in (a-1,a+1,a*2):

            if   0<=na<=(10**5) and not arr[na]:

                arr[na]=arr[a]+1

                queue.append(na)

arr=[0]*(10**5+1)

n,k=map(int,input().split())

bfs()