insertion in circular linked list code example

Example 1: circular linked list in c

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

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

struct node *head = NULL;
struct node *current = NULL;

bool isEmpty() {
   return head == NULL;
}

int length() {
   int length = 0;

   //if list is empty
   if(head == NULL) {
      return 0;
   }

   current = head->next;

   while(current != head) {
      length++;
      current = current->next;   
   }
	
   return length;
}

//insert link at the first location
void insertFirst(int key, int data) {

   //create a link
   struct node *link = (struct node*) malloc(sizeof(struct node));
   link->key = key;
   link->data = data;
	
   if (isEmpty()) {
      head = link;
      head->next = head;
   } else {
      //point it to old first node
      link->next = head;
		
      //point first to new first node
      head = link;
   }    
}

//delete first item
struct node * deleteFirst() {

   //save reference to first link
   struct node *tempLink = head;
	
   if(head->next == head) {  
      head = NULL;
      return tempLink;
   }     

   //mark next to first link as first 
   head = head->next;
	
   //return the deleted link
   return tempLink;
}

//display the list
void printList() {

   struct node *ptr = head;
   printf("\n[ ");
	
   //start from the beginning
   if(head != NULL) {
	
      while(ptr->next != ptr) {     
         printf("(%d,%d) ",ptr->key,ptr->data);
         ptr = ptr->next;
      }
   }
	
   printf(" ]");
}

void main() {
   insertFirst(1,10);
   insertFirst(2,20);
   insertFirst(3,30);
   insertFirst(4,1);
   insertFirst(5,40);
   insertFirst(6,56); 

   printf("Original List: "); 
	
   //print list
   printList();

   while(!isEmpty()) {            
      struct node *temp = deleteFirst();
      printf("\nDeleted value:");  
      printf("(%d,%d) ",temp->key,temp->data);
   }   
	
   printf("\nList after deleting all items: ");
   printList();   
}

Example 2: circular linked list insertion

#include <iostream>

using namespace std;
class node
{
public:
    int data;
    node*next;
};
node*head=NULL;
void insert_begin(int a)
{
    node*temp=new node;
    temp->data=a;
    if(head==NULL)
    {
        temp->next=temp;
        head=temp;
    }
    else
    {
        node*ptr=new node;
        ptr=head;
        while(ptr->next!=head)
        {
           ptr=ptr->next;
        }
        ptr->next=temp;
        temp->next=head;
        head=temp;

    }
}
void insert_end(int a)
{
    node*temp=new node;
    temp->data=a;
    if(head==NULL)
    {
        temp->next=head;
        head=temp;
    }
    else
    {
        node*ptr=new node;
        ptr=head;
        while(ptr->next!=head)
        {
            ptr=ptr->next;
        }
        ptr->next=temp;
        temp->next=head;
    }
}
void printf()
{
    node*temp=new node;
    temp=head;
    do
    {
        cout<<temp->data<<" ";
        temp=temp->next;
    }while(temp!=head);

    cout<<endl;
}

int main()
{
    while(1)
    {
        cout<<"1-insert at begin"<<endl<<"2-insert at end"<<endl<<"3-exit"<<endl;
        int n;
        cout<<"enter your choice:"<<endl;
        cin>>n;
        cout<<"enter thee value you want to insert:"<<endl;
        int val;
        cin>>val;
        switch(n)
        {
        case 1:
            {
                cout<<"enter thee value you want to insert:"<<endl;
                  int val;
                  cin>>val;
                insert_begin(val);
                printf();
                break;
            }
        case 2:
            {
                cout<<"enter thee value you want to insert:"<<endl;
                int val;
                cin>>val;
                insert_end(val);
                printf();
                break;
            }
        case 3:

            {
                exit(0);
            }
        default:
            {
                cout<<"invalid choice :"<<endl;
            }
        }
    }
    return 0;
}