Insertion in circular linked list: Beginning and End

C Program to Insert a node in circular linked list at Beginning

#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
struct node{
	int data;
	struct node *next;
	};
struct node *head=NULL;
struct node* createNode(){
	struct node *newNode = (struct node *)malloc(sizeof(struct node));
    return (newNode);
    }

void insertNodeAtBegin(){
    struct node *newNode, *temp, *ptr1, *ptr2;
    newNode=createNode();
    printf("Enter a data to insert at begining:");
    scanf("%d",&newNode->data);
    newNode->next=NULL;
    if(head==NULL){
	    head=newNode;
	    head->next=head;
    }
    else{
	    ptr1=head;
	    ptr2=head;
	    while(ptr1->next!=head){
		    ptr1=ptr1->next;
	    }
	    ptr1->next=newNode;
	    head=newNode;
	    head->next=ptr2;
    }
}

void viewList(){
	struct node* temp=head;
	if(temp==NULL){
		printf("list is empty");
	}
	else{
	    printf("Data in circular linked list are:\n");
		while(temp->next!=head)
		{
			printf("%d\t",temp->data);
			temp=temp->next;
		}
		printf("%d \t",temp->data);
	}
}

int menu(){
    int choice;
    printf("\n 1. Insert at begining");
    printf("\n 2. Travesre/View List");
    printf("\n 3. exit");
    printf("\n Please enter your choice: \t");
    scanf("%d",&choice);
    return(choice);
}
 void main(){
    while(1){
        switch(menu()){
            case 1:
                insertNodeAtBegin();
                break;
            case 2:
                viewList();
                break;
            case 3:
                exit(0);
            default:
                printf("invalid choice");   
        }
        getch();
    }  
}

Output:

C Program to Insert a node in circular linked list at End

[cc]
#include
#include
#include
struct node{
int data;
struct node *next;
};
struct node *head=NULL;
struct node* createNode(){
struct node *newNode = (struct node *)malloc(sizeof(struct node));
return (newNode);
}

void insertNodeAtEnd(){
struct node *temp,*ptr;
temp=createNode();
printf(“Enter a data to insert at end:”);
scanf(“%d”,&temp->data);
temp->next=NULL;
if(head==NULL){
head=temp;
head->next=head;
}
else{
ptr=head;
while(ptr->next!=head){
ptr=ptr->next;
}
ptr->next=temp;
temp->next=head;
}
}

void viewList(){
struct node* temp=head;
if(temp==NULL){
printf(“list is empty”);
}
else{
printf(“Data in circular linked list are:\n”);
while(temp->next!=head)
{
printf(“%d\t”,temp->data);
temp=temp->next;
}
printf(“%d \t”,temp->data);
}
}

int menu(){
int choice;
printf(“\n 1. Insert at end”);
printf(“\n 2. Travesre/View List”);
printf(“\n 3. exit”);
printf(“\n Please enter your choice: \t”);
scanf(“%d”,&choice);
return(choice);
}
void main(){
while(1){
switch(menu()){
case 1:
insertNodeAtEnd();
break;
case 2:
viewList();
break;
case 3:
exit(0);
default:
printf(“invalid choice”);
}
getch();
}
}
[/cc]

Output: