Singly Linked List

Singly linked list is a list where in every node there are two parts data part and a pointer to the next node in the list hence traversing of list is unidirectional means we can traverse a linked list in one direction. 

In singly linked list first node of the list is pointed by the start or head pointer and there is a NULL value in the next pointer of the last node.

syntax/structure

struct node
{
int data;
struct node *next;
}

Memory representation:

//here upload image for MR.

Menu driven program for singly linked list:

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
struct node
{
int data;
struct node *link;
};
struct node *start=NULL;

//insert node at start
void insertnode_start(int data)
{
 struct node *temp;
 temp=(struct node *)malloc(sizeof(struct node));
 temp->data=data;
 temp->link=NULL;
 if(start==NULL)
 {
     start=temp;
 temp->link=start;
 }
 else
 {
 temp->link=start;
 start=temp;
 }
}

//insert node at end

void insertnode_end(int data)
{
 struct node *cur=start;
 struct node *temp;
 temp=(struct node *)malloc(sizeof(struct node));
 temp->data=data;
 temp->link=NULL;
 if(start==NULL)
 {
     start=temp;
     temp->link=start;
 }
 else
 {
   while(cur->link!=start)
   {
    cur=cur->link;
   }
   cur->link=temp;
   temp->link=start;
 }
}
//insert node at a given location

void insertnode_loc(int loc, int data)
{
 int i;
 struct node *cur=start;
 struct node *temp;
 temp=(struct node *)malloc(sizeof(struct node));
 temp->data=data;
 temp->link=NULL;
 for(i=1;i<loc;i++)
 cur=cur->link;
 if(loc<1 || cur==NULL)
 {
 printf("nWrong Location - Insertion not possible n");
 return;
 }
 temp->link=cur->link;
 cur->link=temp;
}
//delete node at start
void deletenode_start()
{
struct node *cur=start;
if(start==NULL)
{
printf("nLinked is Empty ");
return;
}
start=start->link;
free(cur);
printf("nNode Deleted from Start");
}

//delete node end
void deletenode_end()
{
struct node *cur=start;
struct node *prev;
if(start==NULL)
{
printf("nLinked is Empty ");
return;
}
while(cur->link!=start)
{
prev=cur;
cur=cur->link;
}
prev->link=start;
free(cur);
printf("nNode Deleted from End");
}

//delete node at a given location
void deletenode_loc(int loc)
{
struct node *cur=start;
struct node *prev;
int i;
if(start==NULL)
{
printf("nLinked is Empty ");
return;
}
for(i=1;i<loc;i++)
{
 prev=cur;
 cur=cur->link;
}
if(loc<1 || cur==NULL)
{
 printf("nWrong Location - Deletion not possible n");
 return;
}
prev->link=cur->link;
free(cur);
printf("nNode %d Deleted ",loc);
}

//traverse list
void traverse_llist()
{
 struct node *cur=start;
 if(start==NULL)
 printf("Linked List is empty");
 else
 {
  while(cur!=start)
  {
  printf("%d --->",cur->data);
  cur=cur->link;
  }
 }
}



void main()
{
    int ch;
    int data;
    int l;
    int choice;
    
    do
    {
        printf("nn******** Various Operation on Linked List Data Structure********nn Main Menu:nn");
        printf("n Enter 1 : Add Node to Linked List (Start, End or Location)");
        printf("n Enter 2 : Delete a Node to Linked List (Start, End or Location).");
        printf("n Enter 3 : Traverse all Nodes in Linked List");
        printf("n Enter Any other Key to Exit");
        
        
        printf("nEnter Your Choice: __nn");
        
        scanf("%d", &choice);
        
        switch(choice)
        {
            case 1:
                                    //insert();
                printf("Enter 1: to insert at start/begning nn");
                printf("Enter 2: to insert at end nn");
                printf("Enter 3: to insert in between nodes nn");    
                scanf("%d",&ch);
                switch(ch)
                {
            case 1:
                
            //    insert at start
            printf("Enter a value to addn");
            scanf("%d",&data);
            insertnode_start(data);
        
                
                break;
            case 2:
                // insert at end
                printf("Enter a value to addn");
                scanf("%d",&data);
                insertnode_end(data);
            
                break;
            case 3:
                //insert in between nodes
                printf("Enter the location where you want to add itemn");
                scanf("%d",&l);
                printf("Enter a value to addn");
                scanf("%d",&data);
                insertnode_loc(l,data);
                break;
            default:
                printf("%d:invalid option. try again...n",ch);
        }
                
                break;
            case 2:
                //delete();
                
                    printf("Enter 1: to delete at start/begning nn");
                    printf("Enter 2: to delete at end nn");
                    printf("Enter 3: to delete in between nodes nn");    
                    scanf("%d",&ch);
                switch(ch)
                {
            case 1:
                
            //    delete at start
                deletenode_start();
                break;
            case 2:
                // delete at end
                deletenode_end();
            
                break;
            case 3:
                //delete in between nodes
                printf("Enter the location where you want to delete itemn");
                scanf("%d",&l);
                deletenode_loc(l);
                break;
    
            default:
                printf("%d:invalid option. try again...n",ch);
        }
        
                break;
            case 3:
                traverse_llist();
                break;
            

   default:
                exit(0);
        }
    } while(choice);
}