A single statement Confusing Recursive Solution Anybody Help!!!


  • 0
    L
    void recursiveReverse(struct node** head_ref)
    {
        struct node* first;
        struct node* rest;
          
        /* empty list */
        if (*head_ref == NULL)
           return;   
     
        /* suppose first = {1, 2, 3}, rest = {2, 3} */
        first = *head_ref;  
        rest  = first->next;
     
        /* List has only one node */
        if (rest == NULL)
           return;   
     
        /* reverse the rest list and put the first element at the end */
        recursiveReverse(&rest);
        first->next->next  = first;  
         
        /* tricky step -- see the diagram */
        first->next  = NULL;          
     
        /* fix the head pointer */
        *head_ref = rest;              
    }
    

    This solution is from geeksforgeeks, here's the link http://www.geeksforgeeks.org/write-a-function-to-reverse-the-nodes-of-a-linked-list/

    The last statement about fixing head_ref pointer is confusing me. Let's take an example of 1->2->3

    n first recursion: first=1, rest=2
    in second recursion: first=2, rest=3
    in last recursion: first=3, rest=null

    and from that point we go back, and in each step we assign *headRef=rest
    finally we come back at first step our rest was 2 and we assign *headRef=2
    but we need rest point to 3 not 2.
    I am sure I am missing something here but I could not resolve this please help me out
    if possible with drawings!!!

    Thank you in advance


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