堆排序

 1     inline int heapParent(int index)
 2     {
 3         if(index & 1)
 4             return index >> 1;
 5         return (index >> 1) - 1;
 6     }
 7 
 8     inline int heapLeft(int index)
 9     {
10         return (index << 1) + 1;
11     }
12 
13     inline int heapRight(int index)
14     {
15         return (index << 1) + 2;
16     }
17 
18 
19 void Solution::maxHeapify(vector<int>& vec, int index, int size)
20 {
21     int largest;
22     int lchild = heapLeft(index);
23     int rchild = heapRight(index);
24     if(lchild < size && vec[lchild] > vec[index])
25         largest = lchild;
26     else largest = index;
27     
28     if(rchild < size && vec[rchild] > vec[largest])
29         largest = rchild;
30     
31     if(largest != index)
32     {
33         swap(vec[index], vec[largest]);
34         maxHeapify(vec, largest, size);
35     }
36 }
37 
38 void Solution::buildMaxHeap(vector<int>& vec, int size)
39 {
40     for(int i = size / 2; i >= 0; i--)
41     {
42         maxHeapify(vec, i, size);
43     }
44 }
45 
46 void Solution::heapSort(vector<int>& vec)
47 {
48     int size = vec.size();
49     buildMaxHeap(vec, size);
50     for(int i = size - 1; i > 0; i--)
51     {
52         swap(vec[i], vec[0]);
53         size--;
54         buildMaxHeap(vec, size);
55     }
56 }