Sum of left leaves

# 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 root is None:
            return 0
        if root.left is None and root.right is None:
            return 0
        leftVal = 0
        if root.left and not root.left.left and not root.left.right:
            leftVal = root.left.val
        else:
            leftVal = self.sumOfLeftLeaves(root.left)
        rightVal = self.sumOfLeftLeaves(root.right)

        return leftVal + rightVal

Sum of Left Leaves

---

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

 

Constraints:

• The number of nodes in the tree is in the range [1, 1000].
• -1000 <= Node.val <= 1000