LeetCode#111 二叉树的最小深度 Python

BFS比DFS合适，因为BFS遇到第一个叶子结点就可直接返回结果，而DFS要遍历整棵树
我再写一遍递归和BFS：

1、递归

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def minDepth(self, root: TreeNode) -> int:
    	if not root: return 0
    	leftDepth = self.minDepth(root.left)
    	rightDepth = self.minDepth(root.right)
    	childDepth = min(selfDepth, rightDepth) if leftDepth and rightDepth else leftDepth or rightDepth
    	return childDepth + 1  	

2、BFS

if not root: return 0
queue = [root]
depth = 0
while queue:
	for _ in range(len(queue)):
		cur = queue.pop(0)
		if not cur.left and not cur.right:
			return depth + 1
		if cur.left:
			queue.append(cur.left)
		if cur.right:
			queue.append(cur.right)
	depth += 1