115 lines
2.7 KiB
C
115 lines
2.7 KiB
C
|
|
//Circular Linked List
|
|
//insertion and Deletion at the beginning of the Linked List
|
|
#include <stdio.h>
|
|
#include <stdlib.h>
|
|
|
|
// Structure Definition
|
|
|
|
// 1. Data of Integer type.
|
|
// 2. Pointer to the Next Node .
|
|
struct node {
|
|
int data ;
|
|
struct node *next ;
|
|
} ;
|
|
struct node *head = NULL ;
|
|
// Use tail pointer to avoid traversing the Linked List while inserting of the new created node
|
|
// because after every insertion of a new node we need to point make the last node point to the newly created Node
|
|
struct node *tail = NULL ;
|
|
|
|
void printList(){
|
|
|
|
if(head == NULL)
|
|
{
|
|
printf("\nList is empty");
|
|
return;
|
|
}
|
|
|
|
else{
|
|
printf("\nItem in the Linked List are : ");
|
|
// Initialize the ptr(pointer) with head location .
|
|
struct node *ptr = head ;
|
|
do{
|
|
printf("%d ",ptr->data) ; // Print the value of the Node
|
|
ptr = ptr->next ; // Increment the ptr
|
|
}while(ptr != head); // While Loop until we encounter a Node pointer ptr not pointing to the same location as head .
|
|
|
|
}
|
|
}
|
|
|
|
|
|
void insertBeg(int data){
|
|
// create a link
|
|
struct node *new_node = (struct node*) malloc(sizeof(struct node)) ;
|
|
|
|
if(new_node==NULL){
|
|
printf("\nCannot create the Node");
|
|
return;
|
|
}
|
|
|
|
else{
|
|
new_node->data=data;
|
|
if(head==NULL){
|
|
// making the head and the tail pointer to point to the newly created node
|
|
head = new_node ;
|
|
tail = new_node;
|
|
}
|
|
else{
|
|
// Point the new_node pointer to the current head
|
|
new_node->next = head ;
|
|
head = new_node ;
|
|
}
|
|
|
|
// making the tail pointer to point to the new head
|
|
tail->next=head;
|
|
}
|
|
}
|
|
|
|
// Deletion at the Beginning of the Circular Linked List
|
|
|
|
void deleteBeg(){
|
|
// NO Deletion when list is empty
|
|
if(head == NULL) {
|
|
printf("\ndeletion not possible ( List is empty )");
|
|
return;
|
|
}
|
|
|
|
// There is only one node left in the list
|
|
else if(head == tail)
|
|
{
|
|
free(head);
|
|
head = NULL;
|
|
tail = NULL;
|
|
return;
|
|
}
|
|
|
|
else{
|
|
// Store head location in a temporary Node pointer.
|
|
struct node *temp = head ;
|
|
|
|
head = head->next ;
|
|
tail->next=head;
|
|
|
|
free(temp);
|
|
}
|
|
}
|
|
|
|
int main(){
|
|
|
|
insertBeg(10); // Insert 10 at Beginning
|
|
insertBeg(20); // Insert 20 at Beginning
|
|
insertBeg(30); // Insert 30 at Beginning
|
|
insertBeg(40); // Insert 40 at Beginning
|
|
insertBeg(50); // Insert 50 at Beginning
|
|
insertBeg(60); // Insert 60 at Beginning
|
|
|
|
printList(); // Prints : 60 50 40 30 20 10
|
|
|
|
deleteBeg(); // Delete First Element
|
|
|
|
printList(); // Prints : 50 40 30 20 10
|
|
|
|
return 0 ;
|
|
}
|
|
|