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HeapSort.cpp
69 lines (61 loc) · 1.11 KB
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HeapSort.cpp
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#include<iostream>
int parent(int i) {
return i / 2;
}
int left(int i) {
return 2 * i;
}
int right(int i) {
return 2 * i + 1;
}
template <class T>
struct Heap {
T* arr;
int size;
//int heap_size;
Heap(int* a, int n) {
arr = a;
size = n;
}
};
template<class T>
void maxHeapify(Heap<T>& h, int i) {
// O(lgN)
int l = left(i);
int r = right(i);
int largest = i;
if (l < h.size && h.arr[l] > h.arr[i]) largest = l;
if (r < h.size && h.arr[r] > h.arr[largest]) largest = r;
if (largest != i) {
std::swap(h.arr[i], h.arr[largest]);
maxHeapify(h, largest);
}
}
template<class T>
void buildHeap(Heap<T>&h) {
// O(N)
//h.heap_size = h.size;
for (int i = h.size / 2 - 1; i >= 0; --i)
maxHeapify(h, i);
}
template <class T>
void heapSort(int* arr, int n) {
// O(N lg N)
Heap<T> h(arr, n);
buildHeap(h);
for (int i = h.size - 1; i >= 1; --i) {
std::swap(h.arr[0], h.arr[i]);
--h.size;
maxHeapify(h, 0);
}
}
int main() {
int a[] = {10, -5, 6, 7, -3, 10, -2};
int size = sizeof(a) / sizeof(int);
heapSort<int>(a, size);
/* for (int i = 0; i < size; ++i) {
std::cout << a[i] << " ";
}
*/
return 0;
}