CODEWITHSUNDEEP
cdata-structureslinked-list
user6547375
user6547375

Reputation: 33

Reverse Link List is not printing while using reverse iteration method

I am trying to print the link list in reverse order but when I run it it's not printing it out. It is just stopping after printing the correct order and the output screen hangs after that. Here's my code:

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
struct node{
    int data;
    struct node *next;
};
void reverse(struct node*);
void main()
{
    struct node *a;
    char ch;
    struct node *temp;
    struct node *temp1;
    a=NULL;
    clrscr();
    do
    {
    if(a==NULL)
    {
        temp=(struct node*)malloc(sizeof(struct node));
        printf("Enter Data");
        scanf("%d",&temp->data);
        temp->next=NULL;
        a=temp;
    }
       else
    {
    temp=(struct node*)malloc(sizeof(struct node));
    temp->next=NULL;
    printf("Enter data element");
    scanf("%d",&temp->data);
    temp1=a;
    while(temp1->next!=NULL)
        {
        temp1=temp1->next;
        }
    temp1->next=temp;
    }
    printf("Do You Wish to continue");
    ch=getch();
    }
    while(ch=='Y'||ch=='y');
    printf("Status of the link list");
    temp1=a;
    while(temp1!=NULL)
    {
    printf("%d ",temp1->data);
    temp1=temp1->next;
    }
    reverse(a);
    getch();
}
void reverse(struct node *head)
{
struct node *prev,*current,*next,*t;
current=head;
prev=NULL;
while(current!=NULL)
    {
    next=current;
    current->next=prev;
    prev=current;
    current=next;
    }
head=prev;
printf("Displaying in reverse order");
t=head;
while(t!=NULL)
    {
    printf("%d",t->data);
    t=t->next;
    }

}

Thanks!

Upvotes: 1

Views: 62

Answers (1)

4386427
4386427

Reputation: 44274

You have two problems with the code.

1) next=current; should be next=current->next; as pointed out by @BLUEPIXY in a comment

2) After calling reverse you have lost your list, i.e. head in main is no longer pointing to head of the list. To fix this you could do:

struct node* reverse(struct node *head)
{
    ....
    return head;
}

and in main

head = reverse(head);

Another solution is:

void reverse(struct node **head) { ... }
                          ^
                          notice

// Called from main as: reverse(&head);

and then dereference head before use in the function. This will make changes to *head in the function to change head in main.

BTW: Don't cast the value returned by malloc

Upvotes: 4

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