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sum-of-left-leaves.py
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sum-of-left-leaves.py
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# Time: O(n)
# Space: O(h)
# 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.
# 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):
"""
:type root: TreeNode
:rtype: int
"""
def sumOfLeftLeavesHelper(root, is_left):
if not root:
return 0
if not root.left and not root.right:
return root.val if is_left else 0
return sumOfLeftLeavesHelper(root.left, True) + \
sumOfLeftLeavesHelper(root.right, False)
return sumOfLeftLeavesHelper(root, False)