LeetCode #404: Sum of Left Leaves

Problem Statement

3
/ \
9  20
/  \
15   7

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

Solution

# 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 helper(self, root):
if not root:
return 0
elif not root.left and not root.right:
return root.val
else:
return self.sumOfLeftLeaves(root)

def sumOfLeftLeaves(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if not root:
return 0
else:
return self.helper(root.left) + self.sumOfLeftLeaves(root.right)