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:
def __init__(self, x):
self.val = x
self.left = None
self.right = None
class Solution:
def sumOfLeftLeaves(self, root):
"""
:type root: TreeNode
:rtype: int
"""
if root is None:
return 0
res = 0
def preorder(root):
nonlocal res
if root.left:
if root.left.left is None and root.left.right is None:
res += root.left.val
if root.left:
preorder(root.left)
if root.right:
preorder(root.right)
preorder(root)
return res