# [Solved] 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.

## Question

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

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 = 
Output: 0
```

Constraints:

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

## 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:
if root==None:return 0
stack = [[root,'']]
s = 0

while stack:
curr,kaha_se = stack.pop()
if not curr.left and not curr.right and kaha_se=='l':s+=int(curr.val)
if curr.left: stack.append([curr.left,'l'])
if curr.right: stack.append([curr.right,'r'])

return s``` ##### Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

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