> For the complete documentation index, see [llms.txt](https://gl01.gitbook.io/gfg-editorials/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gl01.gitbook.io/gfg-editorials/2024/02-2024-feb-15/18-sum-of-leaf-nodes-in-bst.md).

# 18. Sum of leaf nodes in BST

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/sum-of-leaf-nodes-in-bst/1)

## My Approach

* If the root is null, it returns 0.
* If the root has no left and right children (i.e., it's a leaf node), it returns the value of that node.
* Otherwise, it recursively calls itself on the left and right subtrees and returns the sum of the results.

## Time and Auxiliary Space Complexity

* **Time Complexity** : `O(N)`, where `N` is the number of nodes in the Binary Search Tree.
* **Auxiliary Space Complexity** : `O(H)`, where `H` is the height of the Binary Search Tree.

## Code (C++)

```cpp
class Solution {
public:
    int sumOfLeafNodes(Node *root) {
        if (!root)
            return 0;
        
        if (!root->left && !root->right)
            return root->data;
        
        return sumOfLeafNodes(root->left) + sumOfLeafNodes(root->right);
    }
};
```

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