/*
* Sorts LIST according to LESS given auxiliary data AUX, using a
* natural iterative merge sort that runs in O(n lg n) time and
* O(1) space in the number of elements in LIST.
*/
void
list_sort (struct list *list, list_less_func *less, void *aux)
{
size_t output_run_cnt; /* Number of runs output in current pass. */
ASSERT (list != NULL);
ASSERT (less != NULL);
/*
* Pass over the list repeatedly, merging adjacent runs of
* nondecreasing elements, until only one run is left.
*/
do
{
struct list_elem *a0; /* Start of first run. */
struct list_elem *a1b0; /* End of first run, start of second. */
struct list_elem *b1; /* End of second run. */
output_run_cnt = 0;
for (a0 = list_begin (list); a0 != list_end (list); a0 = b1)
{
/* Each iteration produces one output run. */
output_run_cnt++;
/* Locate two adjacent runs of nondecreasing elements
A0...A1B0 and A1B0...B1. */
a1b0 = find_end_of_run (a0, list_end (list), less, aux);
if (a1b0 == list_end (list))
break;
b1 = find_end_of_run (a1b0, list_end (list), less, aux);
/* Merge the runs. */
inplace_merge (a0, a1b0, b1, less, aux);
}
}
while (output_run_cnt > 1);
ASSERT (is_sorted (list_begin (list), list_end (list), less, aux));
}
struct list_elem*
list_find (struct list *list, list_less_func *less, void *aux)
{
struct list_elem *a0;
struct list_elem *a0b0;
a0 = list_head (list);
if(list_empty(list))
return NULL;
a0b0 = find_end_of_run (a0, list_end (list), less, aux);
if (a0b0 == list_end(list))
return NULL;
else
return a0b0;
}
