Description
https://leetcode.com/problems/sum-of-left-leaves/
Given the root of a binary tree, return the sum of all left leaves.
Example 1:
Input: root = [3,9,20,null,null,15,7] Output: 24 Explanation: There are two left leaves in the binary tree, with values 9 and 15 respectively.
Example 2:
Input: root = [1] Output: 0
Constraints:
- The number of nodes in the tree is in the range
[1, 1000]. -1000 <= Node.val <= 1000
Explanation
Traverse and only sum the left leaves.
Python Solution
# 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: TreeNode) -> int:
self.sum_left = 0
self.traverse(root, False)
return self.sum_left
def traverse(self, root, is_left):
if not root:
return
if is_left and not root.left and not root.right:
self.sum_left += root.val
self.traverse(root.left, True)
self.traverse(root.right, False)
- Time Complexity: O(N).
- Space Complexity: O(N).