// here the sorting happens exclusive of the end node
// returns the head node after sorting the linked list
struct node *quickSortRecur(struct node *head, struct node *end)
{
// base condition
if (!head || head == end)
return head;
node *newHead = NULL, *newEnd = NULL;
// Partition the list, newHead and newEnd will be updated
// by the partition function
struct node *pivot = partition(head, end, &newHead, &newEnd);
// If pivot is the smallest element - no need to recur for
// the left part.
if (newHead != pivot)
{
// Set the node before the pivot node as NULL
struct node *tmp = newHead;
while (tmp->next != pivot)
tmp = tmp->next;
tmp->next = NULL;
// Recur for the list before pivot
newHead = quickSortRecur(newHead, tmp);
// Change next of last node of the left half to pivot
tmp = getTail(newHead);
tmp->next = pivot;
}
// Recur for the list after the pivot element
pivot->next = quickSortRecur(pivot->next, newEnd);
return newHead;
}
struct node *quickSortRecur(struct node *head, struct node *end) {
if(!head || head == end) {
return head;
}
node *newHead = NULL, *newEnd = NULL;
struct node *pivot = partition(head, end, &newHead, &newEnd);
if(newHead != pivot) {
struct node *tmp = newHead;
while(tmp->next != pivot) {
tmp = tmp->next;
}
tmp->next = NULL;
newHead = quickSortRecur(newHead, tmp);
}
pivot->next = quickSortRecur(pivot->next, newEnd);
return newHead;
}
// The main function for quick sort. This is a wrapper over recursive
// function quickSortRecur()
void quickSort(struct node **headRef)
{
(*headRef) = quickSortRecur(*headRef, getTail(*headRef));
return;
}
