leetcode【104】Maximum Depth of Binary Tree

版权声明：本文为博主原创文章，未经允许，不得转载，如需转载请注明出处 https://blog.csdn.net/ssjdoudou/article/details/83692501

写在最前面：null

leetcode【104】Maximum Depth of Binary Tree

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7],

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3

通过递归实现

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

class Solution:
    def maxDepth(self, root):
        """
        :type root: TreeNode
        :rtype: int
        """
        if not root:
            return 0
        left = Solution.maxDepth(self,root.left)
        right = Solution.maxDepth(self,root.right)
        if left == 0 and right != 0:
            left = left + 1
        if right == 0 and left != 0:
            right = right + 1
        return max(left, right) + 1