AcWing BFS相关问题 1100. 抓住那头牛

import sys
sys.stdin = open('data.txt', 'r')

'''
简单BFS找最短路长度
'''

from collections import deque
m, n = map(int, input().split())

def bfs(m, n):
    que = deque()
    que.append(m)
    visited = {m}
    step = 0

    while len(que) > 0:

        node_num = len(que)
        for _ in range(node_num):
            cur = que.popleft()

            if cur-1 >= 0 and cur-1 not in visited:
                if cur-1 == n:
                    return step+1

                visited.add(cur-1)
                que.append(cur-1)

            if cur < n:
                if cur+1 not in visited:
                    if cur+1 == n:
                        return step+1

                    visited.add(cur + 1)
                    que.append(cur + 1)

                if cur * 2 not in visited:
                    if cur*2 == n:
                        return step+1

                    visited.add(cur * 2)
                    que.append(cur * 2)

        step += 1
    return -1

print(bfs(m, n))