Quick Sort using Linked list

struct node
{
    int data;
    struct node *link;
    struct node *plink;
};
struct node *first=NULL, *last=NULL;
void swap(struct node* a,struct node* b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}
 
void qsort(struct node *low, struct node *high)
{
    if(low==NULL || high==NULL || low == high || low->plink == high)
    return ;
 
    struct node *pivot=low, *tmp=low->link;
    while(tmp != high->link)
    {
            if(tmp->data < low->data)
            {
                    swap(pivot->link, tmp);
                    pivot = pivot->link;
            }
            tmp = tmp->link;
    }
    swap(low, pivot);
    qsort(low, pivot->plink);
    qsort(pivot->link, high);
}
Quicksort can be implemented for Linked List only when we can pick a fixed point as pivot. Random QuickSort cannot be efficiently implemented for Linked Lists.

Quick Sort using Double Linked list
struct node
{
    int data;
    struct node *next;
    struct node *prev;
};

void swap(struct node* a,struct node* b)
{
    int temp = *a;
    *a = *b;
    *b = temp;
}
 
void qsort(struct node *low, struct node *high)
{
    if(low==NULL || high==NULL || low == high || low->next == high)
    return ;
 
    struct node *pivot=low, *tmp=low->next;
    while(tmp != high-next)
    {
            if(tmp->data < low->data)
            {
                    swap(pivot->next, tmp);
                    pivot = pivot->next;
            }
            tmp = tmp->next;
    }
    swap(low, pivot);
    qsort(low, pivot->previous);
    qsort(pivot->next, high);
}