Sum of Left Leaves

404. Sum of Left Leaves

Difficulty: Easy

Related Topics: Tree, BFS/DFS, Binary Tree

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

A leaf is a node with no children. A left leaf is a leaf that is the left child of another node.

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

Code:

# 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
        else:
            if root.left and root.left.left == None and root.left.right == None:
                return root.left.val + self.sumOfLeftLeaves(root.right)
            else:
                return self.sumOfLeftLeaves(root.left) + self.sumOfLeftLeaves(root.right)

Feedbacks:

I used self.function to directly access to the class. If root.left is the leafnode, I return root.left.val+ recursive of root.right Else, I return self.root.left + self.root.right