1 inline int LEFT(int i)
2 {
3 return (i * 2 + 1);
4 }
5
6 inline int RIGHT(int i)
7 {
8 return (i * 2 + 2);
9 }
10
11 void swap(int &i, int &j)
12 {
13 int temp = i;
14 i = j;
15 j = temp;
16 }
17
18 void max_heapify(int a[], int n, int i)
19 {
20 int left = LEFT(i);
21 int right = RIGHT(i);
22 int max_idx = (left < n && a[i] < a[left]) ? left : i;
23 max_idx = (right < n && a[max_idx] < a[right]) ? right : max_idx;
24 if (i == max_idx) {
25 return;
26 }
27 swap(a[i], a[max_idx]);
28 max_heapify(a, n, max_idx);
29 }
30
31 void build_max_heap(int a[], int n)
32 {
33 for (int i = n / 2 - 1; i >= 0; i--) {
34 max_heapify(a, n, i);
35 }
36 }
37
38 void heap_sort(int a[], int n)
39 {
40 build_max_heap(a, n);
41 for (int i = n - 1; i > 0; i--) {
42 swap(a[i], a[0]);
43 max_heapify(a, i, 0);
44 }
45 }
