/*
 * Copyright (c) 2005-2017 National Technology & Engineering Solutions
 * of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
 * NTESS, the U.S. Government retains certain rights in this software.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *
 *     * Neither the name of NTESS nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
#define SWAP(type, r, s)                                                                           \
  do {                                                                                             \
    type t = r;                                                                                    \
    (r)    = s;                                                                                    \
    (s)    = t;                                                                                    \
  } while (0)

static void siftDown(double *a, int start, int end);

void sort_double(int count, double ra[])
{
  int start, end;

  /* heapify */
  for (start = (count - 2) / 2; start >= 0; start--) {
    siftDown(ra, start, count);
  }

  for (end = count - 1; end > 0; end--) {
    SWAP(double, ra[end], ra[0]);
    siftDown(ra, 0, end);
  }
}

static void siftDown(double *a, int start, int end)
{
  int root = start;

  while (root * 2 + 1 < end) {
    int child = 2 * root + 1;
    if ((child + 1 < end) && (a[child] < a[child + 1])) {
      child += 1;
    }
    if (a[root] < a[child]) {
      SWAP(double, a[child], a[root]);
      root = child;
    }
    else {
      return;
    }
  }
}

void shell_sort(int n, double *arr) { sort_double(n, arr); }
