> 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/2024/05-2024-may-1/06-print-all-nodes-that-dont-have-sibling.md).

# 06. Print all nodes that don't have sibling

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/print-all-nodes-that-dont-have-sibling/1)

## My Approach

* The function noSibling initializes a global vector vec to store the data of nodes that have no siblings.
* It calls the recursive function func to traverse the binary tree in an in-order manner and populate vec with the data of nodes that meet the criteria of having no sibling.
* Within func, if a node has no sibling, its data is pushed into vec.
* After traversal, if vec is empty, it means there are no nodes without siblings, so it adds -1 to vec.
* Finally, it sorts vec in ascending order (if there are elements other than -1) and returns it.

## Time and Auxiliary Space Complexity

* **Time Complexity**: `O(NlogN)`, where `N` is the number of nodes in the tree.
* **Auxiliary Space Complexity**: `O(N)`, due to the recursive calls.

## Code (C++)

```cpp
vector<int>vec;

void func(Node* node)
{
    if (node)
    {
        func(node->left);
        if (node->left && !node->right)
            vec.push_back(node->left->data);
        else if (!node->left && node->right)
            vec.push_back(node->right->data);
        func(node->right);
    }
}

vector<int> noSibling(Node* node)
{
    vec.clear();
    func(node);
    if (vec.empty())
    {
        vec.push_back(-1);
        return vec;
    }
    sort(vec.begin(), vec.end());
    return vec;
}
```

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