# Merge two sorted linked list without duplicates

• Difficulty Level : Easy
• Last Updated : 29 Dec, 2020

Merge two sorted linked list of size n1 and n2. The duplicates in two linked list should be present only once in the final sorted linked list.

Examples:

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```Input : list1: 1->1->4->5->7
list2: 2->4->7->9
Output : 1 2 4 5 7 9```

Approach: Following are the steps:

1. Merge the two sorted linked list in sorted manner. Refer recursive approach of this post. Let the final obtained list be head.

## C++

 `// C++ implementation to merge two sorted linked list``// without duplicates``#include ` `using` `namespace` `std;` `// structure of a node``struct` `Node {``    ``int` `data;``    ``Node* next;``};` `// function to get a new node``Node* getNode(``int` `data)``{``    ``// allocate space``    ``Node* temp = (Node*)``malloc``(``sizeof``(Node));` `    ``// put in data``    ``temp->data = data;``    ``temp->next = NULL;``    ``return` `temp;``}` `// function to merge two sorted linked list``// in a sorted manner``Node* sortedMerge(``struct` `Node* a, ``struct` `Node* b)``{``    ``Node* result = NULL;` `    ``/* Base cases */``    ``if` `(a == NULL)``        ``return` `(b);``    ``else` `if` `(b == NULL)``        ``return` `(a);` `    ``/* Pick either a or b, and recur */``    ``if` `(a->data <= b->data) {``        ``result = a;``        ``result->next = sortedMerge(a->next, b);``    ``}``    ``else` `{``        ``result = b;``        ``result->next = sortedMerge(a, b->next);``    ``}``    ``return` `(result);``}` `/* The function removes duplicates from a sorted list */``void` `removeDuplicates(Node* head)``{``    ``/* Pointer to traverse the linked list */``    ``Node* current = head;` `    ``/* Pointer to store the next pointer of a node to be deleted*/``    ``Node* next_next;` `    ``/* do nothing if the list is empty */``    ``if` `(current == NULL)``        ``return``;` `    ``/* Traverse the list till last node */``    ``while` `(current->next != NULL) {` `        ``/* Compare current node with next node */``        ``if` `(current->data == current->next->data) {` `            ``/* The sequence of steps is important*/``            ``next_next = current->next->next;``            ``free``(current->next);``            ``current->next = next_next;``        ``}``        ``else` `/* This is tricky: only advance if no deletion */``        ``{``            ``current = current->next;``        ``}``    ``}``}` `// function to merge two sorted linked list``// without duplicates``Node* sortedMergeWithoutDuplicates(Node* head1, Node* head2)``{``    ``// merge two linked list in sorted manner``    ``Node* head = sortedMerge(head1, head2);` `    ``// remove duplicates from the list 'head'``    ``removeDuplicates(head);` `    ``return` `head;``}` `// function to print the linked list``void` `printList(Node* head)``{``    ``while` `(head != NULL) {``        ``cout << head->data << ``" "``;``        ``head = head->next;``    ``}``}` `// Driver program to test above``int` `main()``{``    ``// head1: 1->1->4->5->7``    ``Node* head1 = getNode(1);``    ``head1->next = getNode(1);``    ``head1->next->next = getNode(4);``    ``head1->next->next->next = getNode(5);``    ``head1->next->next->next->next = getNode(7);` `    ``// head2: 2->4->7->9``    ``Node* head2 = getNode(2);``    ``head2->next = getNode(4);``    ``head2->next->next = getNode(7);``    ``head2->next->next->next = getNode(9);` `    ``Node* head3;` `    ``head3 = sortedMergeWithoutDuplicates(head1, head2);` `    ``printList(head3);` `    ``return` `0;``}`

## Python3

 `# Python3 implementation to merge two``# sorted linked list without duplicates`` ` `# Structure of a node``class` `Node:``    ` `    ``def` `__init__(``self``, data):``        ` `        ``self``.data ``=` `data``        ``self``.``next` `=` `None`` ` `# Function to get a new node``def` `getNode(data):``    ` `    ``# Allocate space``    ``temp ``=` `Node(data)``    ``return` `temp` `# Function to merge two sorted linked``# list in a sorted manner``def` `sortedMerge(a, b):``    ` `    ``result ``=` `None`` ` `    ``# Base cases``    ``if` `(a ``=``=` `None``):``        ``return``(b)``    ``elif` `(b ``=``=` `None``):``        ``return``(a)`` ` `    ``# Pick either a or b, and recur``    ``if` `(a.data <``=` `b.data):``        ``result ``=` `a``        ``result.``next` `=` `sortedMerge(a.``next``, b)``    ``else``:``        ``result ``=` `b``        ``result.``next` `=` `sortedMerge(a, b.``next``)` `    ``return``(result)``    ` `# The function removes duplicates``# from a sorted list``def` `removeDuplicates(head):` `    ``# Pointer to traverse the linked list``    ``current ``=` `head`` ` `    ``# Pointer to store the next pointer``    ``# of a node to be deleted``    ``next_next ``=` `None`` ` `    ``# Do nothing if the list is empty``    ``if` `(current ``=``=` `None``):``        ``return`` ` `    ``# Traverse the list till last node``    ``while` `(current.``next` `!``=` `None``):`` ` `        ``# Compare current node with next node``        ``if` `(current.data ``=``=` `current.``next``.data):`` ` `            ``# The sequence of steps is important``            ``next_next ``=` `current.``next``.``next``            ``del` `(current.``next``)``            ``current.``next` `=` `next_next``        ``else``:``            ` `            ``# This is tricky: only advance``            ``# if no deletion``            ``current ``=` `current.``next``    ` `# Function to merge two sorted linked list``# without duplicates``def` `sortedMergeWithoutDuplicates(head1, head2):` `    ``# Merge two linked list in sorted manner``    ``head ``=` `sortedMerge(head1, head2)`` ` `    ``# Remove duplicates from the list 'head'``    ``removeDuplicates(head)`` ` `    ``return` `head` `# Function to print the linked list``def` `printList(head):` `    ``while` `(head !``=` `None``):``        ``print``(head.data, end ``=` `' '``)   ``        ``head ``=` `head.``next``    ` `# Driver code``if` `__name__``=``=``'__main__'``:``    ` `    ``# head1: 1.1.4.5.7``    ``head1 ``=` `getNode(``1``)``    ``head1.``next` `=` `getNode(``1``)``    ``head1.``next``.``next` `=` `getNode(``4``)``    ``head1.``next``.``next``.``next` `=` `getNode(``5``)``    ``head1.``next``.``next``.``next``.``next` `=` `getNode(``7``)`` ` `    ``# head2: 2.4.7.9``    ``head2 ``=` `getNode(``2``)``    ``head2.``next` `=` `getNode(``4``)``    ``head2.``next``.``next` `=` `getNode(``7``)``    ``head2.``next``.``next``.``next` `=` `getNode(``9``)`` ` `    ``head3 ``=` `sortedMergeWithoutDuplicates(``        ``head1, head2)`` ` `    ``printList(head3)`` ` `# This code is contributed by rutvik_56`

Output:

`1 2 4 5 7 9`

Time complexity: O(n1 + n2).
Auxiliary Space: O(1).

Exercise: Get the final sorted linked list without duplicates in a single traversal of the two lists.

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