Sum of Left Leaves
# 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: TreeNode) -> int:
return sum_left_node(root, False)
def sum_left_node(root:TreeNode, is_left:bool) -> int:
if root is None:
return 0
if root.left or root.right:
return sum_left_node(root.left, True) + sum_left_node(root.right, False)
else:
if is_left:
return root.val
else:
return 0
用 recursive 解，透過 is_left 當 flag 判斷是否要加該 node 的值