# Sum of left children — Preorder traversal

Easy

Sum of Left Leaves

Easy : https://leetcode.com/problems/sum-of-left-leaves/

Find the sum of all left leaves in a given binary tree.

**Example:**

3

/ \

9 20

/ \

15 7There are two left leaves in the binary tree, with values9and15respectively. Return24.

Iterative Code:

`# Definition for a binary tree node.`

# class TreeNode:

# def __init__(self, val=0…