# Merge two unsorted linked lists to get a sorted list – Set 2

Given two unsorted Linked Lists, L1 of N nodes and L2 of M nodes, the task is to merge them to get a sorted singly linked list.

Examples:

Input: L1 = 3?5?1, L2 = 6?2?4?9
Output: 1?2?3?4?5?6?9

Input: L1 = 1?5?2, L2 = 3?7
Output: 1?2?3?5?7

Note: A Memory Efficient approach that solves this problem in O(1) Auxiliary Space has been approached here,

Approach: The idea is to use an auxiliary array to store the elements of both the linked lists and then sort the array in increasing order. And finally, insert all the elements back into the linked list. Follow the steps below to solve the problem:

Below is an implementation of the above approach:

## C++

 `// C++ program for the above approach``#include ``using` `namespace` `std;` `// Linked list node``class` `Node {``public``:``    ``int` `data;``    ``Node* next;``};` `// Utility function to append key at``// end of linked list``void` `insertNode(Node** head, ``int` `x)``{``    ``Node* ptr = ``new` `Node;``    ``ptr->data = x;``    ``ptr->next = NULL;``    ``if` `(*head == NULL) {``        ``*head = ptr;``    ``}``    ``else` `{``        ``Node* temp;``        ``temp = *head;``        ``while` `(temp->next != NULL) {``            ``temp = temp->next;``        ``}``        ``temp->next = ptr;``    ``}``}` `// Utility function to print linkedlist``void` `display(Node** head)``{``    ``Node* temp;``    ``temp = *head;``    ``if` `(temp == NULL) {``        ``cout << ``"NULL \n"``;``    ``}``    ``else` `{``        ``while` `(temp != NULL) {``            ``cout << temp->data;``            ``if` `(temp->next != NULL)``                ``cout << ``"->"``;``            ``temp = temp->next;``        ``}``    ``}``}` `// Function to merge two linked lists``void` `MergeLinkedlist(Node** head1, Node** head2)``{``    ``Node* ptr;``    ``ptr = *head1;``    ``while` `(ptr->next != NULL) {``        ``ptr = ptr->next;``    ``}` `    ``// Join linked list by placing address of``    ``// first node of L2 in the last node of L1``    ``ptr->next = *head2;``}` `// Function to merge two unsorted linked``// lists to get a sorted list``void` `sortLinkedList(Node** head, Node** head1)``{``    ``// Function call to merge the two lists``    ``MergeLinkedlist(head, head1);` `    ``// Declare a vector``    ``vector<``int``> V;``    ``Node* ptr = *head;` `    ``// Push all elements into vector``    ``while` `(ptr != NULL) {``        ``V.push_back(ptr->data);``        ``ptr = ptr->next;``    ``}` `    ``// Sort the vector``    ``sort(V.begin(), V.end());``    ``int` `index = 0;``    ``ptr = *head;` `    ``// Insert elements in the linked``    ``// list from the vector``    ``while` `(ptr != NULL) {``        ``ptr->data = V[index];``        ``index++;``        ``ptr = ptr->next;``    ``}` `    ``// Display the sorted and``    ``// merged linked list``    ``display(head);``}` `// Driver Code``int` `main()``{``    ``// Given linked list, L1``    ``Node* head1 = NULL;``    ``insertNode(&head1, 3);``    ``insertNode(&head1, 5);``    ``insertNode(&head1, 1);` `    ``// Given linked list, L2``    ``Node* head2 = NULL;``    ``insertNode(&head2, 6);``    ``insertNode(&head2, 2);``    ``insertNode(&head2, 4);``    ``insertNode(&head2, 9);` `    ``// Function Call``    ``sortLinkedList(&head1, &head2);` `    ``return` `0;``}`

## Java

 `// Java program for the above approach``import` `java.util.*;` `class` `GFG {` `    ``// Linked list node``    ``static` `class` `Node {``        ``int` `data;``        ``Node next;``    ``};``    ``static` `Node head1, head2;``  ` `    ``// Utility function to append key at``    ``// end of linked list``    ``static` `Node insertNode(Node head, ``int` `x)``    ``{``        ``Node ptr = ``new` `Node();``        ``ptr.data = x;``        ``ptr.next = ``null``;``        ``if` `(head == ``null``) {``            ``head = ptr;``        ``}``        ``else` `{``            ``Node temp;``            ``temp = head;``            ``while` `(temp.next != ``null``) {``                ``temp = temp.next;``            ``}``            ``temp.next = ptr;``        ``}` `        ``return` `head;``    ``}` `    ``// Utility function to print linkedlist``    ``static` `void` `display(Node head)``    ``{``        ``Node temp;``        ``temp = head;``        ``if` `(temp == ``null``) {``            ``System.out.print(``"null \n"``);``        ``}``        ``else` `{``            ``while` `(temp != ``null``) {``                ``System.out.print(temp.data);``                ``if` `(temp.next != ``null``)``                    ``System.out.print(``"->"``);``                ``temp = temp.next;``            ``}``        ``}``    ``}` `    ``// Function to merge two linked lists``    ``static` `Node MergeLinkedlist()``    ``{``        ``Node ptr;``        ``ptr = head1;``        ``while` `(ptr.next != ``null``) {``            ``ptr = ptr.next;``        ``}` `        ``// Join linked list by placing address of``        ``// first node of L2 in the last node of L1``        ``ptr.next = head2;` `        ``return` `head1;``    ``}` `    ``// Function to merge two unsorted linked``    ``// lists to get a sorted list``    ``static` `void` `sortLinkedList()``    ``{``        ``// Function call to merge the two lists``        ``Node head = MergeLinkedlist();` `        ``// Declare a vector``        ``Vector V = ``new` `Vector<>();``        ``Node ptr = head;` `        ``// Push all elements into vector``        ``while` `(ptr != ``null``) {``            ``V.add(ptr.data);``            ``ptr = ptr.next;``        ``}``        ``Collections.sort(V);``        ``// Sort the vector``        ``;``        ``int` `index = ``0``;``        ``ptr = head;` `        ``// Insert elements in the linked``        ``// list from the vector``        ``while` `(ptr != ``null``) {``            ``ptr.data = V.get(index);``            ``index++;``            ``ptr = ptr.next;``        ``}` `        ``// Display the sorted and``        ``// merged linked list``        ``display(head);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args)``    ``{``        ``// Given linked list, L1` `        ``head1 = insertNode(head1, ``3``);``        ``head1 = insertNode(head1, ``5``);``        ``head1 = insertNode(head1, ``1``);` `        ``// Given linked list, L2``        ``head2 = ``null``;``        ``head2 = insertNode(head2, ``6``);``        ``head2 = insertNode(head2, ``2``);``        ``head2 = insertNode(head2, ``4``);``        ``head2 = insertNode(head2, ``9``);` `        ``// Function Call``        ``sortLinkedList();``    ``}``}` `// This code is contributed by umadevi9616`

## Python3

 `# Py program for the above approach` `# Linked list node``class` `Node:``    ``def` `__init__(``self``, d):``        ``self``.data ``=` `d``        ``self``.``next` `=` `None` `# Utility function to append key at``# end of linked list``def` `insertNode(head, x):``    ``ptr ``=` `Node(x)``    ``if` `(head ``=``=` `None``):``        ``head ``=` `ptr``    ``else``:``        ``temp ``=` `head``        ``while` `(temp.``next` `!``=` `None``):``            ``temp ``=` `temp.``next``        ``temp.``next` `=` `ptr``    ``return` `head` `# Utility function to print linkedlist``def` `display(head):``    ``temp ``=` `head``    ``if` `(temp ``=``=` `None``):``        ``print` `(``"None"``)``    ``else``:``        ``while` `(temp.``next` `!``=` `None``):``            ``print` `(temp.data,end``=``"->"``)``            ``if` `(temp.``next` `!``=` `None``):``                ``print` `("``",end="``")``            ``temp ``=` `temp.``next``        ``print``(temp.data)` `# Function to merge two linked lists``def` `MergeLinkedlist(head1, head2):``    ``ptr ``=` `head1``    ``while` `(ptr.``next` `!``=` `None``):``        ``ptr ``=` `ptr.``next` `    ``# Join linked list by placing address of``    ``# first node of L2 in the last node of L1``    ``ptr.``next` `=` `head2` `    ``return` `head1` `# Function to merge two unsorted linked``# lists to get a sorted list``def` `sortLinkedList(head1, head2):``    ``# Function call to merge the two lists``    ``head1 ``=` `MergeLinkedlist(head1, head2)` `    ``# Declare a vector``    ``V ``=` `[]``    ``ptr ``=` `head1` `    ``# Push all elements into vector``    ``while` `(ptr !``=` `None``):``        ``V.append(ptr.data)``        ``ptr ``=` `ptr.``next` `    ``# Sort the vector``    ``V ``=` `sorted``(V)``    ``index ``=` `0``    ``ptr ``=` `head1` `    ``# Insert elements in the linked``    ``# list from the vector``    ``while` `(ptr !``=` `None``):``        ``ptr.data ``=` `V[index]``        ``index ``+``=` `1``        ``ptr ``=` `ptr.``next` `    ``# Display the sorted and``    ``# merged linked list``    ``display(head1)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ``# Given linked list, L1``    ``head1 ``=` `None``    ``head1 ``=` `insertNode(head1, ``3``)``    ``head1 ``=` `insertNode(head1, ``5``)``    ``head1 ``=` `insertNode(head1, ``1``)`  `    ``# Given linked list, L2``    ``head2 ``=` `None``    ``head2 ``=` `insertNode(head2, ``6``)``    ``head2 ``=` `insertNode(head2, ``2``)``    ``head2 ``=` `insertNode(head2, ``4``)``    ``head2 ``=` `insertNode(head2, ``9``)` `    ``# Function Call``    ``sortLinkedList(head1, head2)` `# This code is contributed by mohit kumar 29.`

## C#

 `// C# program for the above approach``using` `System;``using` `System.Collections.Generic;` `public` `class` `GFG {` `    ``// Linked list node``public`    `class` `Node {``    ``public`    `int` `data;``    ``public`    `Node next;``    ``};` `    ``static` `Node head1, head2;` `    ``// Utility function to append key at``    ``// end of linked list``    ``static` `Node insertNode(Node head, ``int` `x) {``        ``Node ptr = ``new` `Node();``        ``ptr.data = x;``        ``ptr.next = ``null``;``        ``if` `(head == ``null``) {``            ``head = ptr;``        ``} ``else` `{``            ``Node temp;``            ``temp = head;``            ``while` `(temp.next != ``null``) {``                ``temp = temp.next;``            ``}``            ``temp.next = ptr;``        ``}` `        ``return` `head;``    ``}` `    ``// Utility function to print linkedlist``    ``static` `void` `display(Node head) {``        ``Node temp;``        ``temp = head;``        ``if` `(temp == ``null``) {``            ``Console.Write(``"null \n"``);``        ``} ``else` `{``            ``while` `(temp != ``null``) {``                ``Console.Write(temp.data);``                ``if` `(temp.next != ``null``)``                    ``Console.Write(``"->"``);``                ``temp = temp.next;``            ``}``        ``}``    ``}` `    ``// Function to merge two linked lists``    ``static` `Node MergeLinkedlist() {``        ``Node ptr;``        ``ptr = head1;``        ``while` `(ptr.next != ``null``) {``            ``ptr = ptr.next;``        ``}` `        ``// Join linked list by placing address of``        ``// first node of L2 in the last node of L1``        ``ptr.next = head2;` `        ``return` `head1;``    ``}` `    ``// Function to merge two unsorted linked``    ``// lists to get a sorted list``    ``static` `void` `sortList()``    ``{``      ` `        ``// Function call to merge the two lists``        ``Node head = MergeLinkedlist();` `        ``// Declare a vector``        ``List<``int``> V = ``new` `List<``int``>();``        ``Node ptr = head;` `        ``// Push all elements into vector``        ``while` `(ptr != ``null``) {``            ``V.Add(ptr.data);``            ``ptr = ptr.next;``        ``}``        ``V.Sort();``        ``// Sort the vector``        ``;``        ``int` `index = 0;``        ``ptr = head;` `        ``// Insert elements in the linked``        ``// list from the vector``        ``while` `(ptr != ``null``) {``            ``ptr.data = V[index];``            ``index++;``            ``ptr = ptr.next;``        ``}` `        ``// Display the sorted and``        ``// merged linked list``        ``display(head);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `Main(String[] args)``    ``{``      ` `        ``// Given linked list, L1` `        ``head1 = insertNode(head1, 3);``        ``head1 = insertNode(head1, 5);``        ``head1 = insertNode(head1, 1);` `        ``// Given linked list, L2``        ``head2 = ``null``;``        ``head2 = insertNode(head2, 6);``        ``head2 = insertNode(head2, 2);``        ``head2 = insertNode(head2, 4);``        ``head2 = insertNode(head2, 9);` `        ``// Function Call``        ``sortList();``    ``}``}` `// This code is contributed by umadevi9616 `

## Javascript

 `// Javascript program for the above approach` `// Linked list node``class Node {``    ``constructor(d) {``        ``this``.data = d``        ``this``.next = ``null``    ``}``}` `// Utility function to append key at``// end of linked list``function` `insertNode(head, x) {``    ``ptr = ``new` `Node(x)``    ``if` `(head == ``null``) {``        ``head = ptr``    ``} ``else` `{``        ``temp = head``        ``while` `(temp.next != ``null``) {``            ``temp = temp.next``        ``}``        ``temp.next = ptr``    ``}``    ``return` `head``}` `// Utility function to print linkedlist``function` `display(head) {``    ``let temp = head``    ``if` `(temp == ``null``) {``        ``document.write(``"null"``)``    ``}``    ``else` `{``        ``while` `(temp.next != ``null``) {``            ``document.write(temp.data, end = ``"->"``)``            ``if` `(temp.next != ``null``)``                ``document.write(``""``, end = ``""``)``            ``temp = temp.next``        ``}``        ``document.write(temp.data)``    ``}``}` `// Function to merge two linked lists``function` `MergeLinkedlist(head1, head2) {``    ``let ptr = head1``    ``while` `(ptr.next != ``null``)``        ``ptr = ptr.next` `    ``// Join linked list by placing address of``    ``// first node of L2 in the last node of L1``    ``ptr.next = head2` `    ``return` `head1``}` `// Function to merge two unsorted linked``// lists to get a sorted list``function` `sortLinkedList(head1, head2) {``    ``// Function call to merge the two lists``    ``head1 = MergeLinkedlist(head1, head2)` `    ``// Declare a vector``    ``let V = []``    ``let ptr = head1` `    ``// Push all elements into vector``    ``while` `(ptr != ``null``) {``        ``V.push(ptr.data)``        ``ptr = ptr.next``    ``}` `    ``// Sort the vector``    ``V = V.sort((a, b) => a - b)``    ``index = 0``    ``ptr = head1` `    ``// Insert elements in the linked``    ``// list from the vector``    ``while` `(ptr != ``null``) {``        ``ptr.data = V[index]``        ``index += 1``        ``ptr = ptr.next``    ``}` `    ``// Display the sorted and``    ``// merged linked list``    ``display(head1)``}` `// Driver Code` `// Given linked list, L1``let head1 = ``null``;``head1 = insertNode(head1, 3)``head1 = insertNode(head1, 5)``head1 = insertNode(head1, 1)`  `// Given linked list, L2``let head2 = ``null``head2 = insertNode(head2, 6)``head2 = insertNode(head2, 2)``head2 = insertNode(head2, 4)``head2 = insertNode(head2, 9)` `// Function Call``sortLinkedList(head1, head2)` `// This code is contributed by gfgking`

Output
```1->2->3->4->5->6->9

```

Time Complexity: O((N+M)*log(N+M))
Auxiliary Space: O(N+M)

Another Approach: This code defines a program to merge two unsorted linked lists into a single sorted linked list. The main steps of the program are:

1. Define a class called “Node” to represent a node of a linked list. Each node contains an integer value “data” and a pointer “next” to the next node in the list.
2. Define a utility function called “insertNode” to insert a new node with a given value at the end of a linked list. This function takes two parameters: a reference to a pointer to the head of the list, and the value to be inserted.
3. Define a utility function called “display” to print the elements of a linked list. This function takes a pointer to the head of the list as a parameter and prints the value of each node followed by “->” until the end of the list is reached, and then prints “NULL”.
4. Define a function called “MergeLinkedlist” to merge two linked lists. This function takes two parameters: a reference to a pointer to the head of the first list, and a pointer to the head of the second list. It first finds the last node of the first list and sets its “next” pointer to the head of the second list.
5. Define a function called “sortLinkedList” to merge two unsorted linked lists into a single sorted linked list. This function takes two parameters: pointers to the heads of the two lists. It first calls “MergeLinkedlist” to merge the two lists into a single linked list. Then it creates a vector and pushes all the elements of the merged list into the vector. It sorts the vector using the “sort” function from the <algorithm> library, and then creates a new linked list by inserting the elements of the sorted vector one by one using the “insertNode” function. Finally, it calls “display” to print the sorted linked list.
6. In the main function, two unsorted linked lists are created using “insertNode”. The “sortLinkedList” function is called with these two lists as parameters.

Below is the implementation of the above approach:

## C++

 `#include ``#include ``#include ` `using` `namespace` `std;` `// Linked list node``class` `Node {``public``:``    ``int` `data;``    ``Node* next;``    ``Node(``int` `val) : data(val), next(nullptr) {}``};` `// Utility function to append key at``// end of linked list``void` `insertNode(Node*& head, ``int` `x)``{``    ``Node* ptr = ``new` `Node(x);``    ``if` `(head == nullptr) {``        ``head = ptr;``    ``}``    ``else` `{``        ``Node* temp = head;``        ``while` `(temp->next != nullptr) {``            ``temp = temp->next;``        ``}``        ``temp->next = ptr;``    ``}``}` `// Utility function to print linkedlist``void` `display(Node* head)``{``    ``if` `(head == nullptr) {``        ``cout << ``"NULL"` `<< endl;``    ``}``    ``else` `{``        ``while` `(head != nullptr) {``            ``cout << head->data;``            ``if` `(head->next != nullptr)``                ``cout << ``"->"``;``            ``head = head->next;``        ``}``        ``cout << endl;``    ``}``}` `// Function to merge two linked lists``void` `MergeLinkedlist(Node*& head1, Node* head2)``{``    ``Node* ptr = head1;``    ``while` `(ptr->next != nullptr) {``        ``ptr = ptr->next;``    ``}` `    ``// Join linked list by placing address of``    ``// first node of L2 in the last node of L1``    ``ptr->next = head2;``}` `// Function to merge two unsorted linked``// lists to get a sorted list``void` `sortLinkedList(Node* head1, Node* head2)``{``    ``// Function call to merge the two lists``    ``MergeLinkedlist(head1, head2);` `    ``// Declare a vector``    ``vector<``int``> V;` `    ``// Push all elements into vector``    ``while` `(head1 != nullptr) {``        ``V.push_back(head1->data);``        ``head1 = head1->next;``    ``}` `    ``// Sort the vector``    ``sort(V.begin(), V.end());` `    ``// Insert elements in the linked``    ``// list from the vector``    ``Node* curr = nullptr;``    ``for` `(``int` `i = 0; i < V.size(); i++) {``        ``if` `(i == 0) {``            ``curr = ``new` `Node(V[i]);``            ``head1 = curr;``        ``}``        ``else` `{``            ``curr->next = ``new` `Node(V[i]);``            ``curr = curr->next;``        ``}``    ``}` `    ``// Display the sorted and``    ``// merged linked list``    ``display(head1);``}` `// Driver Code``int` `main()``{``    ``// Given linked list, L1``    ``Node* head1 = nullptr;``    ``insertNode(head1, 3);``    ``insertNode(head1, 5);``    ``insertNode(head1, 1);` `    ``// Given linked list, L2``    ``Node* head2 = nullptr;``    ``insertNode(head2, 6);``    ``insertNode(head2, 2);``    ``insertNode(head2, 4);``    ``insertNode(head2, 9);` `    ``// Function Call``    ``sortLinkedList(head1, head2);` `    ``return` `0;``}``// This code is contributed by rudra1807raj`

## Java

 `import` `java.util.ArrayList;``import` `java.util.Collections;``import` `java.util.List;` `class` `Node {``    ``int` `data;``    ``Node next;` `    ``public` `Node(``int` `val) {``        ``data = val;``        ``next = ``null``;``    ``}``}` `public` `class` `MergeAndSortLinkedLists {``    ``// Utility function to append a node at the end of a linked list``    ``static` `Node insertNode(Node head, ``int` `x) {``        ``Node ptr = ``new` `Node(x);``        ``if` `(head == ``null``) {``            ``head = ptr;``        ``} ``else` `{``            ``Node temp = head;``            ``while` `(temp.next != ``null``) {``                ``temp = temp.next;``            ``}``            ``temp.next = ptr;``        ``}``        ``return` `head;``    ``}` `    ``// Utility function to print a linked list``    ``static` `void` `display(Node head) {``        ``if` `(head == ``null``) {``            ``System.out.println(``"NULL"``);``        ``} ``else` `{``            ``while` `(head != ``null``) {``                ``System.out.print(head.data);``                ``if` `(head.next != ``null``) {``                    ``System.out.print(``"->"``);``                ``}``                ``head = head.next;``            ``}``            ``System.out.println();``        ``}``    ``}` `    ``// Function to merge two linked lists``    ``static` `Node mergeLinkedList(Node head1, Node head2) {``        ``if` `(head1 == ``null``) {``            ``return` `head2;``        ``}` `        ``Node ptr = head1;``        ``while` `(ptr.next != ``null``) {``            ``ptr = ptr.next;``        ``}` `        ``// Join linked list by placing the address of``        ``// the first node of L2 in the last node of L1``        ``ptr.next = head2;` `        ``return` `head1;``    ``}` `    ``// Function to merge two unsorted linked``    ``// lists to get a sorted list``    ``static` `void` `sortLinkedList(Node head1, Node head2) {``        ``// Function call to merge the two lists``        ``head1 = mergeLinkedList(head1, head2);` `        ``if` `(head1 == ``null``) {``            ``System.out.println(``"Empty List"``);``            ``return``;``        ``}` `        ``// Declare a list``        ``List list = ``new` `ArrayList<>();` `        ``// Push all elements into the list``        ``Node current = head1;``        ``while` `(current != ``null``) {``            ``list.add(current.data);``            ``current = current.next;``        ``}` `        ``// Sort the list``        ``Collections.sort(list);` `        ``// Insert elements in the linked list from the list``        ``current = head1;``        ``for` `(``int` `i = ``0``; i < list.size(); i++) {``            ``current.data = list.get(i);``            ``current = current.next;``        ``}` `        ``// Display the sorted and merged linked list``        ``display(head1);``    ``}` `    ``// Driver Code``    ``public` `static` `void` `main(String[] args) {``        ``// Given linked list, L1``        ``Node head1 = ``null``;``        ``head1 = insertNode(head1, ``3``);``        ``head1 = insertNode(head1, ``5``);``        ``head1 = insertNode(head1, ``1``);` `        ``// Given linked list, L2``        ``Node head2 = ``null``;``        ``head2 = insertNode(head2, ``6``);``        ``head2 = insertNode(head2, ``2``);``        ``head2 = insertNode(head2, ``4``);``        ``head2 = insertNode(head2, ``9``);` `        ``// Function Call``        ``sortLinkedList(head1, head2);``    ``}``}`

## Python3

 `# Linked list node``class` `Node:``    ``def` `__init__(``self``, val):``        ``self``.data ``=` `val``        ``self``.``next` `=` `None` `# Utility function to append key at``# end of linked list``def` `insertNode(head, x):``    ``ptr ``=` `Node(x)``    ``if` `head ``is` `None``:``        ``head ``=` `ptr``    ``else``:``        ``temp ``=` `head``        ``while` `temp.``next` `is` `not` `None``:``            ``temp ``=` `temp.``next``        ``temp.``next` `=` `ptr``    ``return` `head` `# Utility function to print linkedlist``def` `display(head):``    ``if` `head ``is` `None``:``        ``print``(``"NULL"``)``    ``else``:``        ``while` `head ``is` `not` `None``:``            ``print``(head.data, end``=``"")``            ``if` `head.``next` `is` `not` `None``:``                ``print``(``"->"``, end``=``"")``            ``head ``=` `head.``next``        ``print``()` `# Function to merge two linked lists``def` `MergeLinkedlist(head1, head2):``    ``ptr ``=` `head1``    ``while` `ptr.``next` `is` `not` `None``:``        ``ptr ``=` `ptr.``next``        ` `    ``# Join linked list by placing address of``    ``# first node of L2 in the last node of L1``    ``ptr.``next` `=` `head2`  `# Function to merge two unsorted linked``# lists to get a sorted list``def` `sortLinkedList(head1, head2):``    ` `    ``# Function call to merge the two lists``    ``MergeLinkedlist(head1, head2)``    ` `    ``# Declare a vector``    ``V ``=` `[]``    ` `    ``# Push all elements into vector``    ``while` `head1 ``is` `not` `None``:``        ``V.append(head1.data)``        ``head1 ``=` `head1.``next``        ` `    ``# Sort the vector``    ``V.sort()``    ` `    ``# Insert elements in the linked``    ``# list from the vector``    ``curr ``=` `None``    ``for` `i ``in` `range``(``len``(V)):``        ``if` `i ``=``=` `0``:``            ``curr ``=` `Node(V[i])``            ``head1 ``=` `curr``        ``else``:``            ``curr.``next` `=` `Node(V[i])``            ``curr ``=` `curr.``next``            ` `            ` `    ``# Display the sorted and``    ``# merged linked list``    ``display(head1)` `# Driver Code``if` `__name__ ``=``=` `'__main__'``:``    ` `    ``# Given linked list, L1``    ``head1 ``=` `None``    ``head1 ``=` `insertNode(head1, ``3``)``    ``head1 ``=` `insertNode(head1, ``5``)``    ``head1 ``=` `insertNode(head1, ``1``)``    ` `    ``# Given linked list, L2``    ``head2 ``=` `None``    ``head2 ``=` `insertNode(head2, ``6``)``    ``head2 ``=` `insertNode(head2, ``2``)``    ``head2 ``=` `insertNode(head2, ``4``)``    ``head2 ``=` `insertNode(head2, ``9``)``    ` `    ``# Function Call``    ``sortLinkedList(head1, head2)` `# This code is contributed by shiv1o43g`

## C#

 `using` `System;``using` `System.Collections.Generic;``using` `System.Linq;` `// Linked list node``class` `Node {``public` `int` `data;``public` `Node next;`  `public` `Node(``int` `val) {``    ``data = val;``    ``next = ``null``;``}``}` `class` `Program {``// Utility function to append key at``// end of linked list``static` `void` `insertNode(``ref` `Node head, ``int` `x) {``Node ptr = ``new` `Node(x);``if` `(head == ``null``) {``head = ptr;``}``else` `{``Node temp = head;``while` `(temp.next != ``null``) {``temp = temp.next;``}``temp.next = ptr;``}``}`  `// Utility function to print linkedlist``static` `void` `display(Node head) {``    ``if` `(head == ``null``) {``        ``Console.WriteLine(``"NULL"``);``    ``}``    ``else` `{``        ``while` `(head != ``null``) {``            ``Console.Write(head.data);``            ``if` `(head.next != ``null``)``                ``Console.Write(``"->"``);``            ``head = head.next;``        ``}``        ``Console.WriteLine();``    ``}``}` `// Function to merge two linked lists``static` `void` `MergeLinkedlist(``ref` `Node head1, Node head2) {``    ``Node ptr = head1;``    ``while` `(ptr.next != ``null``) {``        ``ptr = ptr.next;``    ``}` `    ``// Join linked list by placing address of``    ``// first node of L2 in the last node of L1``    ``ptr.next = head2;``}` `// Function to merge two unsorted linked``// lists to get a sorted list``static` `void` `sortLinkedList(Node head1, Node head2) {``    ``// Function call to merge the two lists``    ``MergeLinkedlist(``ref` `head1, head2);` `    ``// Declare a list``    ``List<``int``> lst = ``new` `List<``int``>();` `    ``// Push all elements into the list``    ``while` `(head1 != ``null``) {``        ``lst.Add(head1.data);``        ``head1 = head1.next;``    ``}` `    ``// Sort the list``    ``lst.Sort();` `    ``// Insert elements in the linked``    ``// list from the list``    ``Node curr = ``null``;``    ``for` `(``int` `i = 0; i < lst.Count; i++) {``        ``if` `(i == 0) {``            ``curr = ``new` `Node(lst[i]);``            ``head1 = curr;``        ``}``        ``else` `{``            ``curr.next = ``new` `Node(lst[i]);``            ``curr = curr.next;``        ``}``    ``}` `    ``// Display the sorted and``    ``// merged linked list``    ``display(head1);``}` `// Driver Code``static` `void` `Main(``string``[] args) {``    ``// Given linked list, L1``    ``Node head1 = ``null``;``    ``insertNode(``ref` `head1, 3);``    ``insertNode(``ref` `head1, 5);``    ``insertNode(``ref` `head1, 1);` `    ``// Given linked list, L2``    ``Node head2 = ``null``;``    ``insertNode(``ref` `head2, 6);``    ``insertNode(``ref` `head2, 2);``    ``insertNode(``ref` `head2, 4);``    ``insertNode(``ref` `head2, 9);` `    ``// Function Call``    ``sortLinkedList(head1, head2);` `    ``Console.ReadLine();``}``}``//This code is contributed by rudra1807raj`

## Javascript

 `class Node {``    ``constructor(val) {``        ``this``.data = val;``        ``this``.next = ``null``;``    ``}``}` `// Utility function to append a node at the end of a linked list``function` `insertNode(head, x) {``    ``const ptr = ``new` `Node(x);``    ``if` `(head === ``null``) {``        ``head = ptr;``    ``} ``else` `{``        ``let temp = head;``        ``while` `(temp.next !== ``null``) {``            ``temp = temp.next;``        ``}``        ``temp.next = ptr;``    ``}``    ``return` `head;``}` `// Utility function to print a linked list``function` `display(head) {``    ``if` `(head === ``null``) {``        ``console.log(``"NULL"``);``    ``} ``else` `{``        ``while` `(head !== ``null``) {``            ``process.stdout.write(head.data.toString());``            ``if` `(head.next !== ``null``) {``                ``process.stdout.write(``"->"``);``            ``}``            ``head = head.next;``        ``}``        ``console.log();``    ``}``}` `// Function to merge two linked lists``function` `mergeLinkedList(head1, head2) {``    ``if` `(head1 === ``null``) {``        ``return` `head2;``    ``}` `    ``let ptr = head1;``    ``while` `(ptr.next !== ``null``) {``        ``ptr = ptr.next;``    ``}` `    ``// Join linked list by placing the address of``    ``// the first node of L2 in the last node of L1``    ``ptr.next = head2;` `    ``return` `head1;``}` `// Function to merge two unsorted linked lists to get a sorted list``function` `sortLinkedList(head1, head2) {``    ``// Function call to merge the two lists``    ``head1 = mergeLinkedList(head1, head2);` `    ``if` `(head1 === ``null``) {``        ``console.log(``"Empty List"``);``        ``return``;``    ``}` `    ``// Declare an array``    ``const list = [];` `    ``// Push all elements into the array``    ``let current = head1;``    ``while` `(current !== ``null``) {``        ``list.push(current.data);``        ``current = current.next;``    ``}` `    ``// Sort the array``    ``list.sort();` `    ``// Insert elements in the linked list from the array``    ``current = head1;``    ``for` `(let i = 0; i < list.length; i++) {``        ``current.data = list[i];``        ``current = current.next;``    ``}` `    ``// Display the sorted and merged linked list``    ``display(head1);``}` `// Driver Code` `// Given linked list, L1``let head1 = ``null``;``head1 = insertNode(head1, 3);``head1 = insertNode(head1, 5);``head1 = insertNode(head1, 1);` `// Given linked list, L2``let head2 = ``null``;``head2 = insertNode(head2, 6);``head2 = insertNode(head2, 2);``head2 = insertNode(head2, 4);``head2 = insertNode(head2, 9);` `// Function Call``sortLinkedList(head1, head2);`

Output
```1->2->3->4->5->6->9

```

Time Complexity: The time complexity of the given algorithm is O(n log n) where n is the total number of elements in the two linked lists. This is because the algorithm involves sorting the elements using the sort function, which has a time complexity of O(n log n). In addition, iterating over the linked lists to populate the vector and then the sorted linked list takes O(n) time.

Auxiliary Space: The space complexity of the given algorithm is O(n) where n is the total number of elements in the two linked lists. This is because we are creating a vector of size n to store all the elements of the linked list before sorting. In addition, we are creating a new linked list of size n to store the sorted elements. However, we are not using any extra space proportional to the size of the input beyond the two linked lists and the vector used for sorting, so the space complexity is O(n).

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