# 08. Merge 2 sorted linked lists in reverse order

The problem can be found at the following link: [Question Link](https://www.geeksforgeeks.org/problems/merge-2-sorted-linked-list-in-reverse-order/1)

![](https://badgen.net/badge/Level/Medium/yellow)

## My Approach

* Defined a `reverseList` to reverse a linked list recursively.
* Created a`mergeResult` to merge two sorted linked lists in reverse order.
  * Create a new node `curr` and a `head` node to keep track of the merged list.
  * Traverse both lists, comparing elements and merging them in descending order.
  * Update `curr` as you traverse.
  * After one list is exhausted, append the remaining elements of the other list to `curr`.
  * Return the reversed merged list.

## Time and Auxiliary Space Complexity

* **Time Complexity**: `O(N + M)` where N and M are the lengths of the two linked lists.
* **Auxiliary Space Complexity**: O(1)

## Code (C++)

```cpp
class Solution {
public:
    struct Node *reverseList(Node *curr) {
        if (!curr || !(curr->next))
            return curr;
        auto res = reverseList(curr->next);
        curr->next->next = curr;
        curr->next = NULL;
        return res;
    }

    struct Node *mergeResult(Node *node1, Node *node2) {
        if (!node1)
            return reverseList(node2);
        if (!node2)
            return reverseList(node1);

        Node *curr = new Node;
        Node *head = curr;

        while (node1 && node2) {
            if (node1->data < node2->data) {
                curr->next = node1;
                node1 = node1->next;
            } else {
                curr->next = node2;
                node2 = node2->next;
            }
            curr = curr->next;
        }

        while (node1) {
            curr->next = node1;
            node1 = node1->next;
            curr = curr->next;
        }

        while (node2) {
            curr->next = node2;
            node2 = node2->next;
            curr = curr->next;
        }

        head = head->next;
        return reverseList(head);
    }
};
```

## Contribution and Support

For discussions, questions, or doubts related to this solution, please visit our [discussion section](https://github.com/getlost01/gfg-potd/discussions). We welcome your input and aim to foster a collaborative learning environment.

If you find this solution helpful, consider supporting us by giving a `⭐ star` to the [getlost01/gfg-potd](https://github.com/getlost01/gfg-potd) repository.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://gl01.gitbook.io/gfg-editorials/2024/01-2024-jan-7/08-merge-2-sorted-linked-lists-in-reverse-order.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.