Description

Find the sum of all left leaves in a given binary tree.

Example

3 / \ 9 20 / \ 15 7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.

Explain

判断是否为左子树并且是否不存在子树，都满足则加上这个val ps：才发现leetcode可以加参数= =

Code

# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution(object): def sumOfLeftLeaves(self, root, isleft=False): """ :type root: TreeNode :rtype: int """ if not root: return 0 if not root.left and not root.right: return root.val if isleft else 0 return self.sumOfLeftLeaves(root.left, True) + self.sumOfLeftLeaves(root.right, False)