67 lines
3.1 KiB
C
67 lines
3.1 KiB
C
|
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
||
|
|
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
|
||
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
||
|
|
│ Copyright 2020 Justine Alexandra Roberts Tunney │
|
||
|
|
│ │
|
||
|
|
│ This program is free software; you can redistribute it and/or modify │
|
||
|
|
│ it under the terms of the GNU General Public License as published by │
|
||
|
|
│ the Free Software Foundation; version 2 of the License. │
|
||
|
|
│ │
|
||
|
|
│ This program is distributed in the hope that it will be useful, but │
|
||
|
|
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
|
||
|
|
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
|
||
|
|
│ General Public License for more details. │
|
||
|
|
│ │
|
||
|
|
│ You should have received a copy of the GNU General Public License │
|
||
|
|
│ along with this program; if not, write to the Free Software │
|
||
|
|
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
|
||
|
|
│ 02110-1301 USA │
|
||
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
||
|
|
#include "libc/alg/alg.h"
|
||
|
|
#include "libc/str/str.h"
|
||
|
|
|
||
|
|
static unsigned heapsortmax(int32_t (*A)[2], unsigned n, unsigned i, unsigned j,
|
||
|
|
unsigned k) {
|
||
|
|
unsigned m = i;
|
||
|
|
if (j < n && A[j][0] > A[m][0]) m = j;
|
||
|
|
if (k < n && A[k][0] > A[m][0]) m = k;
|
||
|
|
return m;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void heapsortdown(int32_t (*A)[2], unsigned n, unsigned i) {
|
||
|
|
unsigned j;
|
||
|
|
int32_t t[2];
|
||
|
|
for (;;) {
|
||
|
|
unsigned j = heapsortmax(A, n, i, 2 * i + 1, 2 * i + 2);
|
||
|
|
if (j == i) break;
|
||
|
|
memcpy(t, A[i], sizeof(t));
|
||
|
|
memcpy(A[i], A[j], sizeof(t));
|
||
|
|
memcpy(A[j], t, sizeof(t));
|
||
|
|
i = j;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Sorts key-values.
|
||
|
|
*
|
||
|
|
* heapsortcar is a linearithmic / constant-memory / non-stable sorting
|
||
|
|
* function that's a tenth the size of the more generalized qsort() API.
|
||
|
|
* It can only sort arrays of 64-bit values, and comparisons happen by
|
||
|
|
* treating the lower 32-bits as a signed integer.
|
||
|
|
*
|
||
|
|
* @see test/libc/alg/heapsortcar_test.c
|
||
|
|
*/
|
||
|
|
void heapsortcar(int32_t (*A)[2], unsigned n) {
|
||
|
|
unsigned i;
|
||
|
|
int32_t t[2];
|
||
|
|
for (i = ((n - 2) / 2) + 1; i > 0; i--) {
|
||
|
|
heapsortdown(A, n, i - 1);
|
||
|
|
}
|
||
|
|
for (i = 0; i < n; i++) {
|
||
|
|
memcpy(t, A[n - i - 1], sizeof(t));
|
||
|
|
memcpy(A[n - i - 1], A[0], sizeof(t));
|
||
|
|
memcpy(A[0], t, sizeof(t));
|
||
|
|
heapsortdown(A, n - i - 1, 0);
|
||
|
|
}
|
||
|
|
}
|