Hi, im trying to modify this code to have both forward and backward links
Code:/* ============================================================================ Name : LinkedList.c Author : Version : Copyright : Your copyright notice Description : Hello World in C, Ansi-style ============================================================================ */ # include<stdio.h> # include<conio.h> # include "malloc.h" struct node { int data; struct node *link; }; void main() { int a=111,b=2,c=3,will,wish,num; struct node *ptr,*ptr2,*result,*temp; void add(struct node **,int ); struct node * search(struct node *); void display(struct node *); void invert(struct node *); void del(struct node *,int); struct node * concat(struct node *,struct node *); ptr=NULL; ptr2=NULL; result=NULL; //result for storing the result of concatenation clrscr(); will=1; while(will==1) { printf("Main Menu\n 1. Add element\n 2.Delete element \n 3.Search element\n"); printf("4. Linked List concatenation\n 5.Invert linked list\n 6. Display elements\n"); printf("Please enter the choice"); scanf("%d",&wish); switch(wish) { case 1: printf("Enter the element you want to add "); scanf("%d",&num); add(&ptr,num); display(ptr); break; case 2: printf("Enter the element to delete "); scanf("%d",&num); del(ptr,num); break; case 3: printf("Now demonstrating search "); temp = search(ptr); printf("Address of first occurence is %u ",temp); break; case 4: /* Inputs given internally for demo only */ printf(" Now demonstrating linked list concatenation Press any key to continue..."); add(&ptr2,2); add(&ptr2,4); add(&ptr2,6); getch(); printf("Displaying second Linked List"); display(ptr2); getch(); result = concat(ptr,ptr2); clrscr(); printf("Now Displaying the result of concatenation"); display(result); getch(); break; case 5: printf("Inverting the list ...Press any key to continue..."); invert(ptr); break; case 6: display(ptr); break; default:printf("Illegal choice"); } printf("DO you want to continue ( press 1 for yes "); scanf("%d",&will); } //end of while } void add(struct node **q,int num) { struct node *temp; temp = *q; if(*q==NULL) { *q=malloc(sizeof(struct node)); temp = *q; } else { while((temp->link)!=NULL) { temp=temp->link; } temp->link = malloc(sizeof(struct node)); temp=temp->link; } temp->data = num; temp->link = NULL; } void display(struct node *pt) { while(pt!=NULL) { printf("Data : %d",pt->data); printf("Link : %d",pt->link); pt=pt->link; } } void invert(struct node *ptr) { struct node *p,*q,*r; p=ptr; q=NULL; while(p!=NULL) { r=q; q=p; p=p->link; q->link=r; } ptr = q; display(ptr); } // CONCATENATION OF LINKED LISTS struct node * concat(struct node *p,struct node *q) { struct node *x,*r; if (p==NULL) r=q; if (q==NULL) r=p; else { x=p; r=x; while(x->link!=NULL) x=x->link; x->link=q; } return(r); } // SEARCHING AN ELEMENT IN THE LINKED LIST // THIS FUNCTION FINDS THE FIRST OCCURENCE OF // A DATA AND RETURNS A POINTER TO ITS ADDRESS struct node * search(struct node *p) { struct node *temp; int num; temp = p; printf("Enter the data that you want to search "); scanf("%d",&num); printf("Link of temp %u", temp->link); while(temp->link!=NULL) { printf("In while "); if(temp->data == num) return(temp); temp=temp->link; } return(NULL); } // DELETING DATA FROM THE LINKED LIST// void del(struct node *p,int num) { struct node *temp,*x; temp=p; x= NULL; while (temp->link !=NULL) { if(temp->data == num) { if (x==NULL) { p = temp->link; free(temp); return; } else { x->link = temp->link; free(temp); return; } } //end of outer if x=temp; temp=temp->link; } //end of while printf("No such entry to delete "); } //end of fn.
