//堆排序//①维护堆 void max_heapify(int *ptr,int index,int len){    index = index + 1;    int left = index << 1;    int right = (index << 1) + 1;    int largest = index;    if(left <= len && ptr[left - 1] > ptr[index - 1])        largest = left;    if(right <= len && ptr[right - 1] > ptr[largest - 1])        largest = right;    if(largest != index)    {        swap(&ptr[index - 1],&ptr[largest - 1]);        max_heapify(ptr,largest-1,len);    }    } //②建立堆void build_max_heap(int* ptr,int len){    for(int i = len >> 1; i >= 0; --i)    {        max_heapify(ptr,i,len);     }} //③堆排序void heapSort(int* ptr,int len){    build_max_heap(ptr,len);    for(int i = len - 1;i>0;--i)    {        swap(&ptr[0],&ptr[i]);        max_heapify(ptr,0,i);    }} int main(){    int a[] = {2,23,45,1,8,2,0};     for(int i =0; i <= 6; ++i)    {        std::cout << a[i] << " ";    }    cout << endl;    //mergeSort(a,0,6);    //quickSort(a,0,6);    heapSort(a,7);    for(int i =0; i <= 6; ++i)    {        std::cout << a[i] << " ";    }    std::cout << std::endl;    return 0;}