C Program to Merge two sorted single linked lists

Write a C Program to Merge two sorted single linked lists. Here’s simple Menu Driven Program to Merge two sorted single linked lists in C Programming Language.

What is Linked List ?

Linked list is a linear data structure that contains sequence of elements such that each element links to its next element in the sequence. Each link contains a connection to another link.

Following are the important terms to understand the concept of Linked List.

• Link − Each link of a linked list can store a data called an element.
• Next − Each link of a linked list contains a link to the next link called Next.

Each element in a linked list is called as “Node”. Each node consists of its own data and the address of the next node and forms a chain. Linked Lists are used to create trees and graphs.

Basic Operations

Following are the basic operations supported by a list.

• Insertion − Adds an element at the beginning of the list.
• Deletion − Deletes an element at the beginning of the list.
• Display − Displays the complete list.
• Search − Searches an element using the given key.
• Delete − Deletes an element using the given key.

Below is the source code for C Program to Merge two sorted single linked lists which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/* C Program to Merge two sorted single linked lists*/


#include<stdio.h>
#include<stdlib.h>

struct node
{
        int info;
        struct node *link;
};

struct node *create(struct node *start);
struct node *insert_s(struct node *start,int data);
struct node *insert(struct node *start,int data);
void display(struct node *start );
void merge(struct node *p1,struct node *p2);
int main()
{
        struct node *start1=NULL,*start2=NULL;
        start1=create(start1);
        start2=create(start2);

        printf("List1 : ");
        display(start1);
        printf("List2 : ");
        display(start2);
        merge(start1, start2);

        return 0;

}/*End of main()*/

void merge(struct node *p1,struct node *p2)
{
        struct node *start3;
        start3=NULL;

        while(p1!=NULL && p2!=NULL)
        {
                if(p1->info < p2->info)
                {
                        start3=insert(start3,p1->info);
                        p1=p1->link;
                }
                else if(p2->info < p1->info)
                {
                        start3=insert(start3,p2->info);
                        p2=p2->link;
                }
                else if(p1->info==p2->info)
                {
                        start3=insert(start3,p1->info);
                        p1=p1->link;
                        p2=p2->link;
                }
        }
        /*If second list has finished and elements left in first list*/
        while(p1!=NULL)
        {
                start3=insert(start3,p1->info);
                p1=p1->link;
        }
        /*If first list has finished and elements left in second list*/
        while(p2!=NULL)
        {
                start3=insert(start3,p2->info);
                p2=p2->link;
        }
        printf("Merged list is : ");
        display(start3);
}

struct node *create(struct node *start )
{
        int i,n,data;
        printf("Enter the number of nodes : ");
        scanf("%d",&n);
        start=NULL;
        for(i=1;i<=n;i++)
        {
                printf("Enter the element to be inserted : ");
                scanf("%d",&data);
                start=insert_s(start, data);
        }
        return start;
}/*End of create_slist()*/

struct node *insert_s(struct node *start,int data)
{
        struct node *p,*tmp;
        tmp=(struct node *)malloc(sizeof(struct node));
        tmp->info=data;
        /*list empty or data to be added in beginning */
        if(start==NULL || data<start->info)
        {
                tmp->link=start;
                start=tmp;
                return start;
        }
        else
        {
                p=start;
                while(p->link!=NULL && p->link->info < data)
                        p=p->link;
                tmp->link=p->link;
                p->link=tmp;
        }
        return start;
}/*End of insert_s()*/

struct node *insert(struct node *start,int data)
{
        struct node *p,*tmp;
        tmp=(struct node *)malloc(sizeof(struct node));
        tmp->info=data;
        /*If list is empty*/
        if(start==NULL)
        {
                tmp->link=start;
                start=tmp;
                return start;
        }
        else    /*Insert at the end of the list*/
        {
                p=start;
                while(p->link!=NULL)
                        p=p->link;
                tmp->link=p->link;
                p->link=tmp;
        }
        return start;
}/*End of insert()*/

void display(struct node *start)
{
        struct node *p;
        if(start==NULL)
        {
                printf("List is empty\n");
                return;
        }
        p=start;
        while(p!=NULL)
        {
                printf("%d ",p->info);
                p=p->link;
        }
        printf("\n");
}/*End of display()*/

OUTPUT : :

/* C Program to Merge two sorted single linked lists*/

*************** OUTPUT *********************


Enter the number of nodes : 5
Enter the element to be inserted : 4
Enter the element to be inserted : 1
Enter the element to be inserted : 5
Enter the element to be inserted : 8
Enter the element to be inserted : 6

Enter the number of nodes : 5
Enter the element to be inserted : 1
Enter the element to be inserted : 2
Enter the element to be inserted : 1
Enter the element to be inserted : 3
Enter the element to be inserted : 0

List1 : 1 4 5 6 8

List2 : 0 1 1 2 3

Merged list is : 0 1 1 2 3 4 5 6 8

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