Sum of Left Leaves in Binary Tree

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

A left leaf is a leaf that is the left child of its parent.

Function Signature:

class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right

def sum_of_left_leaves(root: TreeNode) -> int:
    """
    Calculate the sum of all left leaves in a binary tree.

    Parameters:
    - root: The root of the binary tree.

    Returns:
    - int: The sum of all left leaves.
    """
    # Your code here

Example:

# Example Binary Tree:
#        6
#       / \
#      8  12
#        /  \
#       10   5

root = TreeNode(6,
                TreeNode(8),
                TreeNode(12,
                         TreeNode(10),
                         TreeNode(5)
                         )
                )

result = sum_of_left_leaves(root)  
print(result)
assert result == 23
# Explanation: Sum of left leaves: 8 + 10 = 18

Note:

• The given binary tree is not necessarily a binary search tree.
• All node values are unique.

Instructions:

• Write the sum_of_left_leaves function to solve the problem.
• Implement your solution in Python.
• Provide clear comments in your code.
• Discuss the time and space complexity of your solution.

As always, we’ll share our solution to this problem tomorrow. Stay tuned 😊