堆排序-algorithms_3th

 1 #include <iostream>
 2 using namespace std;
 3 
 4 int PARENT(const int &i){
 5     return (i>>2)-1;
 6 }
 7 
 8 int LEFT(const int &i){
 9     return (i<<1)+1;
10 }
11 
12 int RIGHT(const int &i){
13     return (i<<1) + 2;
14 }
15 
16 void MAX_HEAPIFY(int *const A, const int &i,const int &heap_size){
17     int l = LEFT(i);
18     int r = RIGHT(i);
19     int largest=i;
20     if (l < heap_size && A[l]>A[i]){
21         largest = l;
22     }
23     else{
24         largest = i;
25     }
26 
27     if (r<heap_size && A[r]>A[largest]){
28         largest = r;
29     }
30     if (largest != i){
31         int key = A[i];
32         A[i] = A[largest];
33         A[largest] = key;
34         MAX_HEAPIFY(A, largest,heap_size);
35     }
36 }
37 
38 void BUILD_MAX_HEAP(int *const A, const int &heap_size){
39     for (auto i = heap_size / 2; i >= 0; --i){
40         MAX_HEAPIFY(A, i, heap_size);
41     }
42 }
43 
44 void swap2(int &a, int &b){
45     int t = a;
46     a = b;
47     b = t;
48 }
49 
50 void HEAP_SORT(int *const A, int &heap_size){
51     BUILD_MAX_HEAP(A, heap_size);
52     for (auto i = heap_size-1; i > 0; --i){
53         swap2(A[i], A[0]);
54         --heap_size;
55         MAX_HEAPIFY(A, 0, heap_size);
56     }
57 }
58 
59 int main(void)
60 {
61     int a[] = { 16, 4, 10, 14, 7, 9, 3, 2, 8, 1 };
62     int length = end(a) - begin(a);
63     HEAP_SORT(a, length);
64     system("pause");
65     return 0;
66 }