Sum of Left Leaves.py

#!/usr/bin/python

'''
Given the root of a binary tree, return the sum of all left leaves.
'''

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def sumOfLeftLeaves(self, root: Optional[TreeNode]) -> int:
        if not root:
            return 0

        if root.left and not root.left.left and not root.left.right:
            return root.left.val + self.sumOfLeftLeaves(root.right)

        else:
            return self.sumOfLeftLeaves(root.left) + self.sumOfLeftLeaves(root.right)