Merge two sorted linked lists using recursion
The problem at hand involves merging two sorted linked lists using recursion in a C program. Linked lists are a fundamental data structure in computer science used to store and manage collections of elements. A linked list consists of nodes, where each node contains data and a reference (or link) to the next node in the list. In this program, two sorted linked lists are merged into a single sorted linked list using a recursive approach.
Problem Statement
You are given two sorted linked lists, and your task is to merge them into a single sorted linked list using recursion. The resulting linked list should maintain the sorted order of elements.
Idea to Solve
To solve this problem, we will define a recursive function mergeList
that takes two pointers to nodes of
the linked lists as arguments and returns a pointer to the merged list. The function will compare the values of the
nodes and recursively merge the smaller node with the rest of the merged list. We will also define a function
merge
that handles the merging of two linked lists by updating the pointers of the original lists.
Pseudocode
- Define a
LinkNode
structure to represent a node of the linked list with data and a reference to the next node. - Define a
SingleLL
structure to represent the singly linked list with head and tail pointers. - Implement a function
newLinkedList
to create a new linked list. - Implement a function
createLinkNode
to create a new node with the given data. - Implement a function
addNode
to add a new node at the end of the linked list. - Implement a function
display
to display the elements of the linked list. - Implement a function
mergeList
to merge two sorted linked lists recursively.- Base cases:
- If one of the lists is empty, return the other list.
- Recursive cases:
- If the value of the first node in the first list is smaller, set the next of the first node to the result of merging the rest of the first list with the second list.
- Otherwise, do the same with the second list and the first list.
- Return the merged list.
- Base cases:
- Implement a function
merge
to handle the request of merging two sorted linked lists.- Base cases:
- If the second list is empty, return.
- If the first list is empty, set the first list's head and tail pointers to the second list's head and tail pointers.
- Recursive case:
- Merge the first list's head with the result of merging the rest of the first list with the second list.
- Update the tail pointer if necessary.
- Reset the second list's head and tail pointers.
- Base cases:
- In the
main
function:- Create two new linked lists.
- Add elements to the first and second lists, creating two sorted linked lists.
- Display the original lists.
- Merge the second list into the first list using the
merge
function. - Display the merged list.
Code Solution
// C Program
// Merge two sorted linked lists using recursion
#include <stdio.h>
#include <stdlib.h> //for malloc function
// Linked List LinkNode
struct LinkNode
{
int data;
struct LinkNode *next;
};
// Singly linked list
struct SingleLL
{
struct LinkNode *head;
struct LinkNode *tail;
};
// Returns the new linked list
struct SingleLL *newLinkedList()
{
// Create memory of head and tail Nodes
struct SingleLL *sll = (struct SingleLL *) malloc(sizeof(struct SingleLL));
if (sll == NULL)
{
printf("Memory overflow\n");
}
else
{
sll->head = NULL;
sll->tail = NULL;
}
return sll;
}
// Returns a new Node of linked list
struct LinkNode *createLinkNode(int data)
{
// Create dynamic node
struct LinkNode *node = (struct LinkNode *) malloc(sizeof(struct LinkNode));
if (node == NULL)
{
printf("Memory overflow\n");
}
else
{
// Set initial node value
node->data = data;
node->next = NULL;
}
return node;
}
// Add new Node at end of linked list
void addNode(struct SingleLL *sll, int data)
{
struct LinkNode *node = createLinkNode(data);
if (sll->head == NULL)
{
sll->head = node;
}
else
{
// Append the node at last position
sll->tail->next = node;
}
sll->tail = node;
}
// Display linked list element
void display(struct SingleLL *sll)
{
if (sll->head == NULL)
{
printf("\n Empty linked list\n");
return;
}
struct LinkNode *temp = sll->head;
// iterating linked list elements
while (temp != NULL)
{
printf(" %d →", temp->data);
// Visit to next node
temp = temp->next;
}
printf(" NULL\n");
}
// Sorted Merge of two sorted list
struct LinkNode *mergeList(struct LinkNode *l1, struct LinkNode *l2)
{
if (l1 == NULL)
{
// When l1 empty
return l2;
}
else if (l2 == NULL)
{
// When l2 empty
return l1;
}
if (l1->data < l2->data)
{
l1->next = mergeList(l1->next, l2);
return l1;
}
else
{
l2->next = mergeList(l1, l2->next);
return l2;
}
}
// Handles the request of merging two sorted linked list
void merge(struct SingleLL *sll1, struct SingleLL *sll2)
{
if (sll2->head == NULL)
{
// When have no element in second linked list
return;
}
else if (sll1->head == NULL)
{
sll1->head = sll2->head;
sll1->tail = sll2->tail;
}
else
{
sll1->head = mergeList(sll1->head, sll2->head);
if (sll2->tail->data > sll1->tail->data)
{
sll1->tail = sll2->tail;
}
else if (sll1->tail->data == sll2->tail->data)
{
// Set new tail node
struct LinkNode *auxiliary = sll1->head;
while (auxiliary->next != NULL)
{
auxiliary = auxiliary->next;
}
sll1->tail = auxiliary;
}
}
sll2->head = NULL;
sll2->tail = NULL;
}
int main()
{
// Create linked list
struct SingleLL *sll1 = newLinkedList();
struct SingleLL *sll2 = newLinkedList();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
addNode(sll1, 1);
addNode(sll1, 7);
addNode(sll1, 8);
addNode(sll1, 15);
addNode(sll1, 19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
addNode(sll2, -2);
addNode(sll2, 5);
addNode(sll2, 6);
addNode(sll2, 12);
addNode(sll2, 16);
addNode(sll2, 18);
addNode(sll2, 19);
addNode(sll2, 31);
printf("\n First Linked List \n");
display(sll1);
printf("\n Second Linked List \n");
display(sll2);
merge(sll1, sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
printf("\n After Merge \n");
display(sll1);
return 0;
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
/*
Java Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
public int data;
public LinkNode next;
public LinkNode(int data)
{
this.data = data;
this.next = null;
}
}
public class SingleLL
{
public LinkNode head;
public LinkNode tail;
public SingleLL()
{
this.head = null;
this.tail = null;
}
//Add new Node at end of linked list
public void addNode(int data)
{
LinkNode node = new LinkNode(data);
if (this.head == null)
{
this.head = node;
}
else
{
// Append the node at last position
this.tail.next = node;
}
this.tail = node;
}
// Display linked list element
public void display()
{
if (this.head == null)
{
System.out.print("\n Empty linked list\n");
return;
}
LinkNode temp = this.head;
//iterating linked list elements
while (temp != null)
{
System.out.print(" " + temp.data + " →");
// Visit to next node
temp = temp.next;
}
System.out.print(" NULL\n");
}
// Sorted Merge of two sorted list
public LinkNode mergeList(LinkNode l1, LinkNode l2)
{
if (l1 == null)
{
// When l1 empty
return l2;
}
else if (l2 == null)
{
// When l2 empty
return l1;
}
if (l1.data < l2.data)
{
l1.next = mergeList(l1.next, l2);
return l1;
}
else
{
l2.next = mergeList(l1, l2.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
public void merge(SingleLL other)
{
if (other.head == null)
{
// When have no element in second linked list
return;
}
else if (this.head == null)
{
this.head = other.head;
this.tail = other.tail;
}
else
{
this.head = mergeList(this.head, other.head);
if (other.tail.data > this.tail.data)
{
this.tail = other.tail;
}
else if (this.tail.data == other.tail.data)
{
// Set new tail node
LinkNode auxiliary = this.head;
while (auxiliary.next != null)
{
auxiliary = auxiliary.next;
}
this.tail = auxiliary;
}
}
other.head = null;
other.tail = null;
}
public static void main(String[] args)
{
// Create linked list
SingleLL sll1 = new SingleLL();
SingleLL sll2 = new SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
System.out.print("\n First Linked List \n");
sll1.display();
System.out.print("\n Second Linked List \n");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
System.out.print("\n After Merge \n");
sll1.display();
}
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
// Include header file
#include <iostream>
using namespace std;
/*
C++ Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
public:
int data;
LinkNode *next;
LinkNode(int data)
{
this->data = data;
this->next = NULL;
}
};
class SingleLL
{
public:
LinkNode *head;
LinkNode *tail;
SingleLL()
{
this->head = NULL;
this->tail = NULL;
}
//Add new Node at end of linked list
void addNode(int data)
{
LinkNode *node = new LinkNode(data);
if (this->head == NULL)
{
this->head = node;
}
else
{
// Append the node at last position
this->tail->next = node;
}
this->tail = node;
}
// Display linked list element
void display()
{
if (this->head == NULL)
{
cout << "\n Empty linked list\n";
return;
}
LinkNode *temp = this->head;
//iterating linked list elements
while (temp != NULL)
{
cout << " " << temp->data << " →";
// Visit to next node
temp = temp->next;
}
cout << " NULL\n";
}
// Sorted Merge of two sorted list
LinkNode *mergeList(LinkNode *l1, LinkNode *l2)
{
if (l1 == NULL)
{
// When l1 empty
return l2;
}
else if (l2 == NULL)
{
// When l2 empty
return l1;
}
if (l1->data < l2->data)
{
l1->next = this->mergeList(l1->next, l2);
return l1;
}
else
{
l2->next = this->mergeList(l1, l2->next);
return l2;
}
}
// Handles the request of merging two sorted linked list
void merge(SingleLL *other)
{
// When have no element in second linked list
if (other->head == NULL)
{
return;
}
else if (this->head == NULL)
{
this->head = other->head;
this->tail = other->tail;
}
else
{
this->head = this->mergeList(this->head, other->head);
if (other->tail->data > this->tail->data)
{
this->tail = other->tail;
}
else if (this->tail->data == other->tail->data)
{
// Set new tail node
LinkNode *auxiliary = this->head;
while (auxiliary->next != NULL)
{
auxiliary = auxiliary->next;
}
this->tail = auxiliary;
}
}
other->head = NULL;
other->tail = NULL;
}
};
int main()
{
// Create linked list
SingleLL sll1 = SingleLL();
SingleLL sll2 = SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
cout << "\n First Linked List \n";
sll1.display();
cout << "\n Second Linked List \n";
sll2.display();
sll1.merge(&sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
cout << "\n After Merge \n";
sll1.display();
return 0;
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
// Include namespace system
using System;
/*
C# Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
public class LinkNode
{
public int data;
public LinkNode next;
public LinkNode(int data)
{
this.data = data;
this.next = null;
}
}
public class SingleLL
{
public LinkNode head;
public LinkNode tail;
public SingleLL()
{
this.head = null;
this.tail = null;
}
//Add new Node at end of linked list
public void addNode(int data)
{
LinkNode node = new LinkNode(data);
if (this.head == null)
{
this.head = node;
}
else
{
// Append the node at last position
this.tail.next = node;
}
this.tail = node;
}
// Display linked list element
public void display()
{
if (this.head == null)
{
Console.Write("\n Empty linked list\n");
return;
}
LinkNode temp = this.head;
//iterating linked list elements
while (temp != null)
{
Console.Write(" " + temp.data + " →");
// Visit to next node
temp = temp.next;
}
Console.Write(" NULL\n");
}
// Sorted Merge of two sorted list
public LinkNode mergeList(LinkNode l1, LinkNode l2)
{
if (l1 == null)
{
// When l1 empty
return l2;
}
else if (l2 == null)
{
// When l2 empty
return l1;
}
if (l1.data < l2.data)
{
l1.next = mergeList(l1.next, l2);
return l1;
}
else
{
l2.next = mergeList(l1, l2.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
public void merge(SingleLL other)
{
// When have no element in second linked list
if (other.head == null)
{
return;
}
else if (this.head == null)
{
this.head = other.head;
this.tail = other.tail;
}
else
{
this.head = mergeList(this.head, other.head);
if (other.tail.data > this.tail.data)
{
this.tail = other.tail;
}
else if (this.tail.data == other.tail.data)
{
// Set new tail node
LinkNode auxiliary = this.head;
while (auxiliary.next != null)
{
auxiliary = auxiliary.next;
}
this.tail = auxiliary;
}
}
other.head = null;
other.tail = null;
}
public static void Main(String[] args)
{
// Create linked list
SingleLL sll1 = new SingleLL();
SingleLL sll2 = new SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
Console.Write("\n First Linked List \n");
sll1.display();
Console.Write("\n Second Linked List \n");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
Console.Write("\n After Merge \n");
sll1.display();
}
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
<?php
/*
Php Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
public $data;
public $next;
function __construct($data)
{
$this->data = $data;
$this->next = null;
}
}
class SingleLL
{
public $head;
public $tail;
function __construct()
{
$this->head = null;
$this->tail = null;
}
//Add new Node at end of linked list
public function addNode($data)
{
$node = new LinkNode($data);
if ($this->head == null)
{
$this->head = $node;
}
else
{
// Append the node at last position
$this->tail->next = $node;
}
$this->tail = $node;
}
// Display linked list element
public function display()
{
if ($this->head == null)
{
echo "\n Empty linked list\n";
return;
}
$temp = $this->head;
//iterating linked list elements
while ($temp != null)
{
echo " ". $temp->data ." →";
// Visit to next node
$temp = $temp->next;
}
echo " NULL\n";
}
// Sorted Merge of two sorted list
public function mergeList($l1, $l2)
{
if ($l1 == null)
{
// When l1 empty
return $l2;
}
else if ($l2 == null)
{
// When l2 empty
return $l1;
}
if ($l1->data < $l2->data)
{
$l1->next = $this->mergeList($l1->next, $l2);
return $l1;
}
else
{
$l2->next = $this->mergeList($l1, $l2->next);
return $l2;
}
}
// Handles the request of merging two sorted linked list
public function merge($other)
{
// When have no element in second linked list
if ($other->head == null)
{
return;
}
else if ($this->head == null)
{
$this->head = $other->head;
$this->tail = $other->tail;
}
else
{
$this->head = $this->mergeList($this->head, $other->head);
if ($other->tail->data > $this->tail->data)
{
$this->tail = $other->tail;
}
else if ($this->tail->data == $other->tail->data)
{
// Set new tail node
$auxiliary = $this->head;
while ($auxiliary->next != null)
{
$auxiliary = $auxiliary->next;
}
$this->tail = $auxiliary;
}
}
$other->head = null;
$other->tail = null;
}
}
function main()
{
// Create linked list
$sll1 = new SingleLL();
$sll2 = new SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
$sll1->addNode(1);
$sll1->addNode(7);
$sll1->addNode(8);
$sll1->addNode(15);
$sll1->addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
$sll2->addNode(-2);
$sll2->addNode(5);
$sll2->addNode(6);
$sll2->addNode(12);
$sll2->addNode(16);
$sll2->addNode(18);
$sll2->addNode(19);
$sll2->addNode(31);
echo "\n First Linked List \n";
$sll1->display();
echo "\n Second Linked List \n";
$sll2->display();
$sll1->merge($sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
echo "\n After Merge \n";
$sll1->display();
}
main();
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
/*
Node Js Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
constructor(data)
{
this.data = data;
this.next = null;
}
}
class SingleLL
{
constructor()
{
this.head = null;
this.tail = null;
}
//Add new Node at end of linked list
addNode(data)
{
var node = new LinkNode(data);
if (this.head == null)
{
this.head = node;
}
else
{
// Append the node at last position
this.tail.next = node;
}
this.tail = node;
}
// Display linked list element
display()
{
if (this.head == null)
{
process.stdout.write("\n Empty linked list\n");
return;
}
var temp = this.head;
//iterating linked list elements
while (temp != null)
{
process.stdout.write(" " + temp.data + " →");
// Visit to next node
temp = temp.next;
}
process.stdout.write(" NULL\n");
}
// Sorted Merge of two sorted list
mergeList(l1, l2)
{
if (l1 == null)
{
// When l1 empty
return l2;
}
else if (l2 == null)
{
// When l2 empty
return l1;
}
if (l1.data < l2.data)
{
l1.next = this.mergeList(l1.next, l2);
return l1;
}
else
{
l2.next = this.mergeList(l1, l2.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
merge(other)
{
// When have no element in second linked list
if (other.head == null)
{
return;
}
else if (this.head == null)
{
this.head = other.head;
this.tail = other.tail;
}
else
{
this.head = this.mergeList(this.head, other.head);
if (other.tail.data > this.tail.data)
{
this.tail = other.tail;
}
else if (this.tail.data == other.tail.data)
{
// Set new tail node
var auxiliary = this.head;
while (auxiliary.next != null)
{
auxiliary = auxiliary.next;
}
this.tail = auxiliary;
}
}
other.head = null;
other.tail = null;
}
}
function main()
{
// Create linked list
var sll1 = new SingleLL();
var sll2 = new SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
process.stdout.write("\n First Linked List \n");
sll1.display();
process.stdout.write("\n Second Linked List \n");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
process.stdout.write("\n After Merge \n");
sll1.display();
}
main();
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
# Python 3 Program for
# Merge two sorted linked lists using recursion
# Linked list node
class LinkNode :
def __init__(self, data) :
self.data = data
self.next = None
class SingleLL :
def __init__(self) :
self.head = None
self.tail = None
# Add new Node at end of linked list
def addNode(self, data) :
node = LinkNode(data)
if (self.head == None) :
self.head = node
else :
# Append the node at last position
self.tail.next = node
self.tail = node
# Display linked list element
def display(self) :
if (self.head == None) :
print("\n Empty linked list")
return
temp = self.head
# iterating linked list elements
while (temp != None) :
print("", temp.data ,"→", end = "")
# Visit to next node
temp = temp.next
print(" NULL")
# Sorted Merge of two sorted list
def mergeList(self, l1, l2) :
if (l1 == None) :
# When l1 empty
return l2
elif(l2 == None) :
# When l2 empty
return l1
if (l1.data < l2.data) :
l1.next = self.mergeList(l1.next, l2)
return l1
else :
l2.next = self.mergeList(l1, l2.next)
return l2
# Handles the request of merging two sorted linked list
def merge(self, other) :
if (other.head == None) :
# When have no element in second linked list
return
elif(self.head == None) :
self.head = other.head
self.tail = other.tail
else :
self.head = self.mergeList(self.head, other.head)
if (other.tail.data > self.tail.data) :
self.tail = other.tail
elif(self.tail.data == other.tail.data) :
# Set new tail node
auxiliary = self.head
while (auxiliary.next != None) :
auxiliary = auxiliary.next
self.tail = auxiliary
other.head = None
other.tail = None
def main() :
# Create linked list
sll1 = SingleLL()
sll2 = SingleLL()
# Sorted linked list 1
# 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1)
sll1.addNode(7)
sll1.addNode(8)
sll1.addNode(15)
sll1.addNode(19)
# Sorted linked list 2
# -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2)
sll2.addNode(5)
sll2.addNode(6)
sll2.addNode(12)
sll2.addNode(16)
sll2.addNode(18)
sll2.addNode(19)
sll2.addNode(31)
print("\n First Linked List ")
sll1.display()
print("\n Second Linked List ")
sll2.display()
sll1.merge(sll2)
# -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
print("\n After Merge ")
sll1.display()
if __name__ == "__main__": main()
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
# Ruby Program for
# Merge two sorted linked lists using recursion
# Linked list node
class LinkNode
# Define the accessor and reader of class LinkNode
attr_reader :data, :next
attr_accessor :data, :next
def initialize(data)
self.data = data
self.next = nil
end
end
class SingleLL
# Define the accessor and reader of class SingleLL
attr_reader :head, :tail
attr_accessor :head, :tail
def initialize()
self.head = nil
self.tail = nil
end
# Add new Node at end of linked list
def addNode(data)
node = LinkNode.new(data)
if (self.head == nil)
self.head = node
else
# Append the node at last position
self.tail.next = node
end
self.tail = node
end
# Display linked list element
def display()
if (self.head == nil)
print("\n Empty linked list\n")
return
end
temp = self.head
# iterating linked list elements
while (temp != nil)
print(" ", temp.data ," →")
# Visit to next node
temp = temp.next
end
print(" NULL\n")
end
# Sorted Merge of two sorted list
def mergeList(l1, l2)
if (l1 == nil)
# When l1 empty
return l2
elsif(l2 == nil)
# When l2 empty
return l1
end
if (l1.data < l2.data)
l1.next = self.mergeList(l1.next, l2)
return l1
else
l2.next = self.mergeList(l1, l2.next)
return l2
end
end
# Handles the request of merging two sorted linked list
def merge(other)
if (other.head == nil)
# When have no element in second linked list
return
elsif(self.head == nil)
self.head = other.head
self.tail = other.tail
else
self.head = self.mergeList(self.head, other.head)
if (other.tail.data > self.tail.data)
self.tail = other.tail
elsif(self.tail.data == other.tail.data)
# Set new tail node
auxiliary = self.head
while (auxiliary.next != nil)
auxiliary = auxiliary.next
end
self.tail = auxiliary
end
end
other.head = nil
other.tail = nil
end
end
def main()
# Create linked list
sll1 = SingleLL.new()
sll2 = SingleLL.new()
# Sorted linked list 1
# 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1)
sll1.addNode(7)
sll1.addNode(8)
sll1.addNode(15)
sll1.addNode(19)
# Sorted linked list 2
# -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2)
sll2.addNode(5)
sll2.addNode(6)
sll2.addNode(12)
sll2.addNode(16)
sll2.addNode(18)
sll2.addNode(19)
sll2.addNode(31)
print("\n First Linked List \n")
sll1.display()
print("\n Second Linked List \n")
sll2.display()
sll1.merge(sll2)
# -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
print("\n After Merge \n")
sll1.display()
end
main()
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
/*
Scala Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode(var data: Int , var next: LinkNode)
{
def this(data: Int)
{
this(data, null);
}
}
class SingleLL(var head: LinkNode , var tail: LinkNode)
{
def this()
{
this(null, null);
}
//Add new Node at end of linked list
def addNode(data: Int): Unit = {
var node: LinkNode = new LinkNode(data);
if (this.head == null)
{
this.head = node;
}
else
{
// Append the node at last position
this.tail.next = node;
}
this.tail = node;
}
// Display linked list element
def display(): Unit = {
if (this.head == null)
{
print("\n Empty linked list\n");
return;
}
var temp: LinkNode = this.head;
//iterating linked list elements
while (temp != null)
{
print(" " + temp.data + " →");
// Visit to next node
temp = temp.next;
}
print(" NULL\n");
}
// Sorted Merge of two sorted list
def mergeList(l1: LinkNode, l2: LinkNode): LinkNode = {
if (l1 == null)
{
// When l1 empty
return l2;
}
else if (l2 == null)
{
// When l2 empty
return l1;
}
if (l1.data < l2.data)
{
l1.next = this.mergeList(l1.next, l2);
return l1;
}
else
{
l2.next = this.mergeList(l1, l2.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
def merge(other: SingleLL): Unit = {
// When have no element in second linked list
if (other.head == null)
{
return;
}
else if (this.head == null)
{
this.head = other.head;
this.tail = other.tail;
}
else
{
this.head = this.mergeList(this.head, other.head);
if (other.tail.data > this.tail.data)
{
this.tail = other.tail;
}
else if (this.tail.data == other.tail.data)
{
// Set new tail node
var auxiliary: LinkNode = this.head;
while (auxiliary.next != null)
{
auxiliary = auxiliary.next;
}
this.tail = auxiliary;
}
}
other.head = null;
other.tail = null;
}
}
object Main
{
def main(args: Array[String]): Unit = {
// Create linked list
var sll1: SingleLL = new SingleLL();
var sll2: SingleLL = new SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
print("\n First Linked List \n");
sll1.display();
print("\n Second Linked List \n");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
print("\n After Merge \n");
sll1.display();
}
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
/*
Swift 4 Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
var data: Int;
var next: LinkNode? ;
init(_ data: Int)
{
self.data = data;
self.next = nil;
}
}
class SingleLL
{
var head: LinkNode? ;
var tail: LinkNode? ;
init()
{
self.head = nil;
self.tail = nil;
}
//Add new Node at end of linked list
func addNode(_ data: Int)
{
let node: LinkNode? = LinkNode(data);
if (self.head == nil)
{
self.head = node;
}
else
{
// Append the node at last position
self.tail!.next = node;
}
self.tail = node;
}
// Display linked list element
func display()
{
if (self.head == nil)
{
print("\n Empty linked list");
return;
}
var temp: LinkNode? = self.head;
//iterating linked list elements
while (temp != nil)
{
print("", temp!.data ,"→", terminator: "");
// Visit to next node
temp = temp!.next;
}
print(" NULL");
}
// Sorted Merge of two sorted list
func mergeList(_ l1: LinkNode? , _ l2 : LinkNode? )->LinkNode?
{
if (l1 == nil)
{
// When l1 empty
return l2;
}
else if (l2 == nil)
{
// When l2 empty
return l1;
}
if (l1!.data < l2!.data)
{
l1!.next = self.mergeList(l1!.next, l2);
return l1;
}
else
{
l2!.next = self.mergeList(l1, l2!.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
func merge(_ other: SingleLL? )
{
// When have no element in second linked list
if (other!.head == nil)
{
return;
}
else if (self.head == nil)
{
self.head = other!.head;
self.tail = other!.tail;
}
else
{
self.head = self.mergeList(self.head, other!.head);
if (other!.tail!.data > self.tail!.data)
{
self.tail = other!.tail;
}
else if (self.tail!.data == other!.tail!.data)
{
// Set new tail node
var auxiliary: LinkNode? = self.head;
while (auxiliary!.next != nil)
{
auxiliary = auxiliary!.next;
}
self.tail = auxiliary;
}
}
other!.head = nil;
other!.tail = nil;
}
}
func main()
{
// Create linked list
let sll1: SingleLL = SingleLL();
let sll2: SingleLL = SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
print("\n First Linked List ");
sll1.display();
print("\n Second Linked List ");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
print("\n After Merge ");
sll1.display();
}
main();
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
/*
Kotlin Program for
Merge two sorted linked lists using recursion
*/
// Linked list node
class LinkNode
{
var data: Int;
var next: LinkNode ? ;
constructor(data: Int)
{
this.data = data;
this.next = null;
}
}
class SingleLL
{
var head: LinkNode ? ;
var tail: LinkNode ? ;
constructor()
{
this.head = null;
this.tail = null;
}
//Add new Node at end of linked list
fun addNode(data: Int): Unit
{
var node: LinkNode ? = LinkNode(data);
if (this.head == null)
{
this.head = node;
}
else
{
// Append the node at last position
this.tail?.next = node;
}
this.tail = node;
}
// Display linked list element
fun display(): Unit
{
if (this.head == null)
{
print("\n Empty linked list\n");
return;
}
var temp: LinkNode ? = this.head;
//iterating linked list elements
while (temp != null)
{
print(" " + temp.data + " →");
// Visit to next node
temp = temp.next;
}
print(" NULL\n");
}
// Sorted Merge of two sorted list
fun mergeList(l1: LinkNode ? , l2 : LinkNode ? ): LinkNode ?
{
if (l1 == null)
{
// When l1 empty
return l2;
}
else if (l2 == null)
{
// When l2 empty
return l1;
}
if (l1.data < l2.data)
{
l1.next = this.mergeList(l1.next, l2);
return l1;
}
else
{
l2.next = this.mergeList(l1, l2.next);
return l2;
}
}
// Handles the request of merging two sorted linked list
fun merge(other: SingleLL): Unit
{
// When have no element in second linked list
if (other.head == null)
{
return;
}
else if (this.head == null)
{
this.head = other.head;
this.tail = other.tail;
}
else
{
this.head = this.mergeList(this.head, other.head);
if (other.tail!!.data > this.tail!!.data)
{
this.tail = other.tail;
}
else if (this.tail!!.data == other.tail!!.data)
{
// Set new tail node
var auxiliary: LinkNode ? = this.head;
while (auxiliary?.next != null)
{
auxiliary = auxiliary.next;
}
this.tail = auxiliary;
}
}
other.head = null;
other.tail = null;
}
}
fun main(args: Array < String > ): Unit
{
// Create linked list
var sll1: SingleLL = SingleLL();
var sll2: SingleLL = SingleLL();
// Sorted linked list 1
// 1 → 7 → 8 → 15 → 19 → NULL
sll1.addNode(1);
sll1.addNode(7);
sll1.addNode(8);
sll1.addNode(15);
sll1.addNode(19);
// Sorted linked list 2
// -2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
sll2.addNode(-2);
sll2.addNode(5);
sll2.addNode(6);
sll2.addNode(12);
sll2.addNode(16);
sll2.addNode(18);
sll2.addNode(19);
sll2.addNode(31);
print("\n First Linked List \n");
sll1.display();
print("\n Second Linked List \n");
sll2.display();
sll1.merge(sll2);
// -2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
print("\n After Merge \n");
sll1.display();
}
Output
First Linked List
1 → 7 → 8 → 15 → 19 → NULL
Second Linked List
-2 → 5 → 6 → 12 → 16 → 18 → 19 → 31 → NULL
After Merge
-2 → 1 → 5 → 6 → 7 → 8 → 12 → 15 → 16 → 18 → 19 → 19 → 31 → NULL
Time Complexity
The time complexity of merging two sorted linked lists using recursion depends on the number of nodes in the linked lists. In the worst case, where both linked lists have 'n' nodes each, the time complexity is O(n), as each node is processed once. The recursive nature of the algorithm contributes to the overall time complexity of O(n).
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