#ifndef HEAP_SORT
#define HEAP_SORT
#include <vector>
#include <algorithm>

int Parent(int i) { return (i-1)/2;}
int LeftChild(int  i) {return 2*i+1;}
int RightChild(int i) {return 2*i + 2;}

template<typename T>
void HeapifyUp(std::vector<T> & data, int pos){
    int parentPos;

    while (pos > 0) {
        parentPos = Parent(pos);
        if (data[pos] > data[parentPos]) {
            std::swap(data[pos], data[parentPos]);
            pos = parentPos;
        } else {
            pos = 0;
        }
    }
}

template<typename T>
void HeapifyDown(std::vector<T> & data, int pos, int size){
    int left{LeftChild(pos)},
        right{RightChild(pos)},
        tmp{left};

    while (left <= size) {
        if (right <= size and data[left] < data[right]) {
           tmp = right;
        }
        if (data[tmp] > data[pos]) {
             std::swap(data[pos], data[tmp]);
             pos = tmp;
        } else {
             pos = size;
        }
        tmp = left = LeftChild(pos);
        right = RightChild(pos);
    }
}

template<typename T>
void HeapSort(std::vector<T> & data) {
    int i{0};
    int size{static_cast<int>(data.size())-1};

    for(i = 1 ; i < static_cast<int>(data.size()); i++) {
        HeapifyUp(data, i);
    }
   
    while (size > 0) {
       std::swap(data[0], data[size]); 
       size --;
       HeapifyDown(data, 0, size);
    }
}
#endif