leetcode-python-二叉树最大深度

1)BFS，效率一般，内存较优

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def maxDepth(self, root: TreeNode) -> int:
        queue = []
        size = 0
        if not root:
            return 0
        depth=0
        queue.append(root)
        while queue:
            size = len(queue)
            while size >0:
                temp = queue[0]
                del queue[0]
                if temp.left:
                    queue.append(temp.left)
                if temp.right:
                    queue.append(temp.right)
                size -= 1
            depth += 1
        return depth