Thread: Reversing a Linked List

I've been trying to reverse a linked list but I'm not sure if this piece of code that I made does what I think it does. The process in my mind is, create a empty node that will be returned as our reverse linked list. Create a temp node to the head of the original node and have

Code:

temp->next = reverseList

. Finally, have

Code:

reverseList = temp

and

Code:

 head = head->next

These instructions are to be repeated until head equals null

What this function should do is take the linked list and gradually do this

Code:

{}, {2,3,5,6,NUll}    
{2, NULL}, {3,5,6,NULL}     
{3, 2, NULL}, {5,6.NULL}    
{5,3,2,NULL}, {6,NULL}   
{6,5,3,2, NULL}, {}.

At this point head should be empty.

Code:

Node *reverse(Node *head)
{
    if(head == NULL)
    {
        return NULL;
    }
    else if(head->next == NULL)
    {
        return head;
    }
    
    Node *reverseList = NULL;
    
    while(head != NULL)
    { 
       Node *temp = head;
       temp->next = reverseList;
       reverseList = temp;
       head = head->next;
    }
    
    return reverseList;
}

It looks good to me.

Cool but the website that has this challenge said that it produces the wrong answer. HackerRank

You need to save head->next each time since you're changing it.

Code:

Node *reverse(Node *head) {
    if (!head || !head->next) return head;
    Node *revList = NULL, *next = NULL;
    for ( ; head; head = next) { 
       next = head->next;
       head->next = revList;
       revList = head;
    }
    return revList;
}

Ah, I missed that temp is an alias for head somehow. Sorry.

Damn it that was the problem. XD thanks guys.