mirror of
git://git.tartarus.org/simon/puzzles.git
synced 2025-04-20 23:51:29 -07:00
Files
a2f7f962ce
C99 reserves the mem* namespace for future expansion. Some Rockbox targets had issues with memswap() conflicting with another definition, so fix that.
72 lines
1.9 KiB
C
72 lines
1.9 KiB
C
/*
|
|
* Implement arraysort() defined in puzzles.h.
|
|
*
|
|
* Strategy: heapsort.
|
|
*/
|
|
|
|
#include <stddef.h>
|
|
#include <string.h>
|
|
|
|
#include "puzzles.h"
|
|
|
|
#define PTR(i) ((char *)array + size * (i))
|
|
#define SWAP(i,j) swap_regions(PTR(i), PTR(j), size)
|
|
#define CMP(i,j) cmp(PTR(i), PTR(j), ctx)
|
|
|
|
#define LCHILD(i) (2*(i)+1)
|
|
#define RCHILD(i) (2*(i)+2)
|
|
#define PARENT(i) (((i)-1)/2)
|
|
|
|
static void downheap(void *array, size_t nmemb, size_t size,
|
|
arraysort_cmpfn_t cmp, void *ctx, size_t i)
|
|
{
|
|
while (LCHILD(i) < nmemb) {
|
|
/* Identify the smallest element out of i and its children. */
|
|
size_t j = i;
|
|
if (CMP(j, LCHILD(i)) < 0)
|
|
j = LCHILD(i);
|
|
if (RCHILD(i) < nmemb &&
|
|
CMP(j, RCHILD(i)) < 0)
|
|
j = RCHILD(i);
|
|
|
|
if (j == i)
|
|
return; /* smallest element is already where it should be */
|
|
|
|
SWAP(j, i);
|
|
i = j;
|
|
}
|
|
}
|
|
|
|
void arraysort_fn(void *array, size_t nmemb, size_t size,
|
|
arraysort_cmpfn_t cmp, void *ctx)
|
|
{
|
|
size_t i;
|
|
|
|
if (nmemb < 2)
|
|
return; /* trivial */
|
|
|
|
/*
|
|
* Stage 1: build the heap.
|
|
*
|
|
* Linear-time if we do it by downheaping the elements in
|
|
* decreasing order of index, instead of the more obvious approach
|
|
* of upheaping in increasing order. (Also, it means we don't need
|
|
* the upheap function at all.)
|
|
*
|
|
* We don't need to downheap anything in the second half of the
|
|
* array, because it can't have any children to swap with anyway.
|
|
*/
|
|
for (i = PARENT(nmemb-1) + 1; i-- > 0 ;)
|
|
downheap(array, nmemb, size, cmp, ctx, i);
|
|
|
|
/*
|
|
* Stage 2: dismantle the heap by repeatedly swapping the root
|
|
* element (at index 0) into the last position and then
|
|
* downheaping the new root.
|
|
*/
|
|
for (i = nmemb-1; i > 0; i--) {
|
|
SWAP(0, i);
|
|
downheap(array, i, size, cmp, ctx, 0);
|
|
}
|
|
}
|