堆排序

具体解析可参见：http://bubkoo.com/2014/01/14/sort-algorithm/heap-sort/

#include<bits/stdc++.h>
using namespace std;

void heap(int *a, int index, int Size){
    int left = 2*index + 1;
    int right = 2*index + 2;
    int iMAX = index;
    
    if(right < Size && a[iMAX] < a[left]) iMAX = left;
    if(right < Size && a[iMAX] < a[right]) iMAX = right;
    
    if(iMAX != index){
        swap(a[index], a[iMAX]);
        heap(a, iMAX, Size);
    }
}

void buildHeap(int *a, int len){
    int index = (len/2)-1;
    
    for(int i = index; i >= 0; i--){
        heap(a, i, len);
    }
}

void heapSort(int *a, int len){
    buildHeap(a, len);
    for(int i = len; i >= 1; i--){
        swap(a[0], a[i-1]);
        heap(a, 0, i-1);

    }
}

int main(){
    int a[10] = {16, 10, 4, 14, 7, 9, 3, 2, 8, 1};
    
    heapSort(a, 10);
    
    for(int i = 0; i < 10; i++){
        cout << a[i] << ' ';
    }
    
}