题目
Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
Note: A leaf is a node with no children.
解题思路
从根节点开始进行BFS，记录深度，遇到的第一个叶节点就是答案
代码
class Solution:
def minDepth(self, root: TreeNode) -> int:
if not root:
return 0
q = [(root, 1)]
while q:
cur, depth = q.pop(0)
if not cur.left and not cur.right:
return depth
if cur.left:
q.append((cur.left, depth + 1))
if cur.right:
q.append((cur.right, depth + 1))
