C code to implement Linked List with all Operations

Linked List is a collection of node and each node has two parts:- information and pointer to next node.Information part may consist of one or more than one fields.

Here, i have given only programs to implement Linked List with all possible operation. To understand algorithm of every peace of code, check videos on my YouTube channel: Coders Hub

This program will show how to:

1. Append element at the end of linked list
2. Concatenate two linked lists
3. Free all nodes in a linked list
4. Reverse a linked list
5. Delete last element of linked list
6. Delete nth element of linked list

7. Combine two ordered linked list into single ordered link list

8. Find union of two linked lists

9. Find intersection of two linked lists

10. Insert after nth element in a linked list

11. Delete every second element of a linked list

12. Place elements in order in a linked list

13. Calculate sum of data of a linked list

14. calculate number of elements in a linked list

15. Make second copy of a linked list

16. Move node forward to nth positions in a linked list

#include <stdio.h>
#include <conio.h>

typedef struct node{
int info;
struct node *link;
}NODE;
 
NODE* create(NODE *start)//for creating a list
{
 NODE *temp,*t;
 int n,i;
 printf("Enter no of nodes you want to insert:");
 scanf("%d",&n);
 for(i=0;i<n;i++)
 {
  temp=(NODE*) malloc(sizeof(NODE));
  printf("Enter data for node %d:",i+1);
  scanf("%d",&temp->info);
  temp->link=NULL;
  if(start==NULL) 
   start=temp;
  else
  {
   t=start;
   while(t->link!=NULL)
    t=t->link;
   t->link=temp;
  }
 }
 return start;
}

void disp(NODE *start)//for printing a list
{
 NODE *t;
 printf("\nElements of the list:");
 for(t=start;t!=NULL;t=t->link)
 {
  if(t->link!=NULL)
   printf("%d->",t->info);
  else
   printf("%d",t->info);
 }
 printf("\n");
}

NODE* append(NODE *start)//append element at end
{
 NODE *t,*temp;
 temp=(NODE*) malloc(sizeof(NODE));
 printf("Enter data to be appended:");
 scanf("%d",&temp->info);
 for(t=start;t->link!=NULL;t=t->link);
 t->link=temp;
 temp->link=NULL;
 return start;
}

NODE* concat(NODE *s1,NODE *s2)//concatenate 2 lists
{
 NODE *t;
 t=s1;
 while(t->link!=NULL)
  t=t->link;
 t->link=s2;
 return s1;
}
 
NODE* fr(NODE *start)//free all nodes in a list
{
 NODE *t;
 t=start;
 while(t!=NULL)
 {
  t=start;
  start=t->link;
  free(t);
 }
 return start;
} 

NODE* rev(NODE *start)//to reverse a list
{ 
 NODE *t1,*t2,*s;
 for(t1=start;t1->link!=NULL;t1=t1->link);
 s=t1;
 while(t1!=start)
 { 
  for(t2=start;t2->link!=t1;t2=t2->link);
  t1->link=t2;
  t1=t2;
 }
 t1->link=NULL;
 return s;
}

NODE* dellast(NODE *start)//delete last element
{
 NODE *t,*t2;
 for(t=start;t->link->link!=NULL;t=t->link);
 t2=t->link;
 free(t2);
 t->link=NULL;
 return start;
}

NODE* deln(NODE *start)//delete nth element
{
 int i=1,n;
 NODE *t,*t2;
 printf("\nEnter pos no of element to be deleted:");
 scanf("%d",&n);
 t=start;
 if(n!=1)
 {
  while(i<n-1)
  {
   t=t->link;
   i++;
  }
  t2=t->link;
  t->link=t2->link;
  free(t2);
 }
 else
 {
  start=t->link;
  free(t);
 }
 return start;
}
NODE* sort(NODE*);
//to combine 2 ordered lists into a single ordered list
NODE* comb(NODE *s1,NODE *s2)
{
 s1=concat(s1,s2);
 s1=sort(s1);
 return s1;
}
 
NODE* uni(NODE *s1,NODE *s2)//to find the union of 2 lists
{
 NODE *s3,*t,*t2,*t3,*temp;
 int flag=1;
 s3=(NODE*) malloc(sizeof(NODE));
 s3=NULL;
 t=s1;
 while(t!=NULL)
 {
  temp=(NODE*) malloc(sizeof(NODE));
  temp->info=t->info;
  temp->link=NULL;
  if(s3==NULL)
   s3=temp;
  else
  {
   t2=s3;
   while(t2->link!=NULL)
    t2=t2->link;
   t2->link=temp;
  }
  t=t->link;
 }
 
 t2=s2;
 while(t2!=NULL)
 {
  t=s1;
  flag=1;
  while(t!=NULL)
  {
   if(t->info==t2->info)
   {
    flag=0;
    break;
   }
   t=t->link;
  }
  if(flag==1)
  {
   for(t3=s3;t3->link!=NULL;t3=t3->link);
   temp=(NODE*) malloc(sizeof(NODE));
   temp->info=t2->info;
   t3->link=temp;
   temp->link=NULL;
  }   
  t2=t2->link;
 }
 return s3;
}

NODE* inter(NODE *s1,NODE *s2)//to find the intersection of 2 lists
{
 NODE *s3,*t1,*t2,*t3,*temp;
 s3=(NODE*) malloc(sizeof(NODE));
 s3=NULL;
 t1=s1;
 while(t1!=NULL)
 {
  t2=s2;
  while(t2!=NULL)
  {
   if(t1->info==t2->info)
   {
    temp=(NODE*) malloc(sizeof(NODE));
    temp->info=t1->info;
    temp->link=NULL;
    if(s3==NULL)
     s3=temp;
    else
    {
     for(t3=s3;t3->link!=NULL;t3=t3->link);
     t3->link=temp;
    }
    break;
   }
   t2=t2->link;
  }
  t1=t1->link;
 }  
 return s3;
} 

NODE* insertn(NODE *s)//to insert at nth position
{
 NODE *t,*t2,*temp;
 int n,i=1;
 printf("Enter data:");
 temp=(NODE*) malloc(sizeof(NODE));
 scanf("%d",&temp->info);
 printf("Enter position no at which element has to be inserted:");
 scanf("%d",&n);
 t=s;
 if(n!=1)
 {
  while(i<n-1)
  {
   t=t->link;
   i++;
  }
  t2=t->link;
  t->link=temp;
  temp->link=t2;
 }
 else
 {
  temp->link=s;
  s=temp;
 }
 return s;
}
  
NODE* del2(NODE *s)//delete every 2nd element in a list
{
 NODE *t1,*t2;
 t1=s;
 while(t1!=NULL)
 {
  t2=t1->link;
  t1->link=t2->link;
  free(t2);
  t1=t1->link;
 }
 return s;
} 

NODE* sort(NODE *s)//to place elements in increasing order
{
 NODE *t1,*t2;
 int temp;
 for(t1=s;t1->link!=NULL;t1=t1->link)
 {
  for(t2=t1->link;t2!=NULL;t2=t2->link)
  {
   if(t1->info>t2->info)
   {
    temp=t1->info;
    t1->info=t2->info;
    t2->info=temp;
   }
  }
 }
 return s;
}

int sum(NODE *s)//to find the sum of elements in a list
{
 int sum=0;
 NODE *t;
 for(t=s;t!=NULL;t=t->link)
  sum+=t->info;
 return sum;
}

int elements(NODE *s)//to find the number of elements in a list
{
 int n=0;
 NODE *t;
 for(t=s;t!=NULL;t=t->link)
  n++;
 return n;
}

NODE* copy(NODE *s1)//to make a second copy of the list
{
 NODE *s2,*t,*temp,*t2;
 s2=NULL;
 t=s1;
 while(t!=NULL)
 {
  temp=(NODE*) malloc(sizeof(NODE));
  temp->info=t->info;
  temp->link=NULL;
  if(s2==NULL)
   s2=temp;
  else
  {
   t2=s2;
   while(t2->link!=NULL)
    t2=t2->link;
   t2->link=temp;
  }
  t=t->link;
 }
 return s2;
} 
   
NODE* forward(NODE *s)//to forward a node by n positions
{
 NODE *t1,*t2,*t3;
 int n1,n2,i;
 printf("Enter position of the node you want to move:");
 scanf("%d",&n1);
 printf("Enter no of positions you want to move:");
 scanf("%d",&n2);
  t1=s;
  i=1;
  while(i<n1)
  {
   t1=t1->link;
   i++;
  }
  t2=s;
  i=1;
  while(i<n1+n2)
  {
   t2=t2->link;
   i++;
  }
  t3=s;
  if(t1!=s)
  while(t3->link!=t1)
   t3=t3->link;
  t3->link=t1->link;
  if(t1==s)
   s=s->link;
  t1->link=t2->link;
  t2->link=t1; 
 return s;
} 

  
void main()
{
 NODE *s1,*s2;
 int ch;
 s1=NULL;
 s2=NULL;
 while(1)
 {
  clrscr();
  printf("Enter choice:\n");
  printf(" 1.Append element at end\n 2.Concatinate two lists\n");
  printf(" 3.Free all nodes in a list\n 4.Reverse a list\n");
  printf(" 5.Delete last element\n 6.Delete nth element\n");
  printf(" 7.Combine two ordered list into single ordered list\n");
  printf(" 8.Find union of two lists\n 9.Find intersection of two lists\n");
  printf("10.Insert after nth element\n11.Delete every second element\n");
  printf("12.Place elements in order\n13.Return sum of data\n");
  printf("14.Return number of elements\n15.Make second copy of list\n");
  printf("16.Move node forward to n positions\n17.Exit\n");
  scanf("%d",&ch);
  clrscr();
  if(ch>0&&ch<=16)
   s1=create(s1);
   disp(s1);
  switch(ch)
  {
   case 1:s1=append(s1);break;
   case 2:s2=create(s2);disp(s2);s1=concat(s1,s2);break;

   case 3:s1=fr(s1);
   printf("List freed\n");
   disp(s1);
   break;
   
   case 4:s1=rev(s1);break;
   case 5:s1=dellast(s1);break;
   case 6:s1=deln(s1);break;
   case 7:s2=create(s2);disp(s2);s1=comb(s1,s2);break;
   case 8:s2=create(s2);disp(s2);s1=uni(s1,s2);break;
   case 9:s2=create(s2);disp(s2);s1=inter(s1,s2);break;
   case 10:s1=insertn(s1);break;
   case 11:s1=del2(s1);break;
   case 12:s1=sort(s1);break;
   case 13:printf("Sum of elements=%d",sum(s1));break;
   case 14:printf("Number of elements=%d",elements(s1));break;
   
   case 15:
   s2=copy(s1);
   printf("Second list:\n");
   disp(s2);
   break;
   
   case 16:s1=forward(s1);break;
   case 17:exit(0);break;
   default:printf("Wrong choice.Enter again");break;
  }
  if(ch!=3&&ch!=13&&ch!=14&&ch!=15&&ch>0&&ch<=16)
  {
   printf("\nResult:");
   disp(s1);
  }
   s1=fr(s1);
   s2=fr(s2);
   getch();
 }   
}

The above code is very easy to understand and if you have any problem in this program, simply comment....


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