HeapSort

void HeapAdjust(int a[], int n, int i) {
  int l = 2*i + 1;
  int r = l + 1;
  int largest = i;

  if (l < n && a[l] > a[i]) {
    largest = l;
  }

  if (r < n && a[r] > a[largest]) {
    largest = r;
  }

  if (largest != i) {
    int t = a[largest];
    a[largest] = a[i];
    a[i] = t;
    HeapAdjust(a, n, largest);
  }
}


void HeapBuild(int a[], int n) {
  for (int i = n/2 - 1; i >= 0; i--) {
    HeapAdjust(a, n, i);
  }
}


void HeapSort(int a[], int n) {
  HeapBuild(a, n);

  for (int i = (n-1); i > 0; i--) {
    int t = a[i];
    a[i] = a[0];
    a[0] = t;
    HeapAdjust(a, i, 0);
  }
}

void Test(void) {
  int a[5] = {1, 9, 2, 4, 3};
  HeapSort(a, 5);
  for (int i = 0; i < 5; i++) {
    printf("%d ", a[i]);
  }
  printf("\n");
  system("pause");
}