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