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Commit d8caa4f

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doubly linkedlist efficient version
1 parent 0d0adad commit d8caa4f

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2 files changed

+126
-143
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2 files changed

+126
-143
lines changed
Lines changed: 125 additions & 143 deletions
Original file line numberDiff line numberDiff line change
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// A complete working C program to demonstrate all insertion methods
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#include <stdio.h>
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#include <stdlib.h>
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// A linked list node
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struct Node {
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int data;
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struct Node* next;
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struct Node* prev;
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};
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/* Given a reference (pointer to pointer) to the head of a list
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and an int, inserts a new node on the front of the list. */
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void push(struct Node** head_ref, int new_data)
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{
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/* 1. allocate node */
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struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
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/* 2. put in the data */
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new_node->data = new_data;
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/* 3. Make next of new node as head and previous as NULL */
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new_node->next = (*head_ref);
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new_node->prev = NULL;
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/* 4. change prev of head node to new node */
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if ((*head_ref) != NULL)
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(*head_ref)->prev = new_node;
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/* 5. move the head to point to the new node */
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(*head_ref) = new_node;
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}
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/* Given a node as prev_node, insert a new node after the given node */
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void insertAfter(struct Node* prev_node, int new_data)
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{
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/*1. check if the given prev_node is NULL */
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if (prev_node == NULL) {
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printf("the given previous node cannot be NULL");
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return;
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}
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/* 2. allocate new node */
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struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
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/* 3. put in the data */
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new_node->data = new_data;
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/* 4. Make next of new node as next of prev_node */
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new_node->next = prev_node->next;
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/* 5. Make the next of prev_node as new_node */
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prev_node->next = new_node;
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/* 6. Make prev_node as previous of new_node */
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new_node->prev = prev_node;
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/* 7. Change previous of new_node's next node */
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if (new_node->next != NULL)
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new_node->next->prev = new_node;
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}
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/* Given a reference (pointer to pointer) to the head
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of a DLL and an int, appends a new node at the end */
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void append(struct Node** head_ref, int new_data)
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{
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/* 1. allocate node */
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struct Node* new_node = (struct Node*)malloc(sizeof(struct Node));
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struct Node* last = *head_ref; /* used in step 5*/
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/* 2. put in the data */
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new_node->data = new_data;
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/* 3. This new node is going to be the last node, so
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make next of it as NULL*/
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new_node->next = NULL;
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/* 4. If the Linked List is empty, then make the new
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node as head */
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if (*head_ref == NULL) {
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new_node->prev = NULL;
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*head_ref = new_node;
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return;
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}
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/* 5. Else traverse till the last node */
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while (last->next != NULL)
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last = last->next;
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/* 6. Change the next of last node */
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last->next = new_node;
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/* 7. Make last node as previous of new node */
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new_node->prev = last;
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return;
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}
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// This function prints contents of linked list starting from the given node
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void printList(struct Node* node)
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{
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struct Node* last;
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printf("\nTraversal in forward direction \n");
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while (node != NULL) {
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printf(" %d ", node->data);
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last = node;
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node = node->next;
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}
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printf("\nTraversal in reverse direction \n");
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while (last != NULL) {
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printf(" %d ", last->data);
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last = last->prev;
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}
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}
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/* Drier program to test above functions*/
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int main()
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{
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/* Start with the empty list */
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struct Node* head = NULL;
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// Insert 6. So linked list becomes 6->NULL
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append(&head, 6);
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// Insert 7 at the beginning. So linked list becomes 7->6->NULL
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push(&head, 7);
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// Insert 1 at the beginning. So linked list becomes 1->7->6->NULL
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push(&head, 1);
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// Insert 4 at the end. So linked list becomes 1->7->6->4->NULL
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append(&head, 4);
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// Insert 8, after 7. So linked list becomes 1->7->8->6->4->NULL
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insertAfter(head->next, 8);
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printf("Created DLL is: ");
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printList(head);
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getchar();
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return 0;
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#include<stdio.h>
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struct node
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{
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int data;
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struct node *link;
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};
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struct node *start=NULL;
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main()
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{
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int choice;
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struct node *q;
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while(1)
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{
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q=(struct node*)malloc(sizeof(struct node));
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q->link=NULL;
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printf("\n1.insertatend\n2.insertatbeg\n3.delfront\n4.delrear\n5.display\n6.free\n");
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printf("enter the choice\n");
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scanf("%d",&choice);
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switch(choice)
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{
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case 1:insertatend(q);
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printf("\n INSERTION SUCCESSFUL\n");
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break;
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case 2:insertatbeg(q);
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printf("\n INSERTION SUCCESSFUL\n");
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break;
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case 3:delfront();
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break;
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case 4:delrear();
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break;
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case 5:display();
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break;
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case 6:freed();
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break;
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default:printf("\n invalid choice\n");
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}
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}
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}
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void insertatend(struct node *q)
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{
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struct node *r;
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printf("\nenter the data which you want to store\n");
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scanf("%d",&q->data);
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if(start==NULL)
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{
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start=q;
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}
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else
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{
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r=start;
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while(r->link!=NULL)
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r=r->link;
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r->link=q;
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}
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}
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void insertatbeg(struct node *q)
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{
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printf("\nenter the data which you want to store\n");
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scanf("%d",&q->data);
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if(start==NULL)
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start=q;
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else
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{
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q->link=start;
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start=q;
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}
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}
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void delfront()
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{
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struct node *r;
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if(start==NULL)
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printf("\nthe list is empty\n");
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else
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{
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r=start;
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start=start->link;
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printf("the deleted element is %d",r->data);
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free(r);
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}
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}
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void delrear()
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{
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struct node *r,*s;
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int count=0,i;
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r=start;
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if(start==NULL)
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printf("\nthe list is empty\n");
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else
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{
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while(r->link!=NULL)
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{
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r=r->link;
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count++;
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}
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printf("the deleted element is %d",r->data);
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free(r);
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s=start;
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for(i=1;i<=count-1;i++)
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{
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s=s->link;
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}
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s->link=NULL;
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}
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}
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void display()
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{
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struct node *r;
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if(start==NULL)
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printf("\nthe list is empty\n");
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else
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{
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r=start;
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while(r!=NULL)
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{
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printf("\t%d\t",r->data);
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r=r->link;
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}
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}
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}
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freed()
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{
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free(start);
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}
Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
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This is a doubly linkedlist program made in c language, it uses the concept of structure,pointer,dynamic memory allocation etc.

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