Heap Sort
Heap is a nearly complete binary tree. we can easily implement on basic array object.
Heap Structure satisfies Heap Property
Heap Property
max-heap-property: Parent's Key $\geq$ Children's key
min-heap-property: Parent's Key $\leq$ Children's key
Implementation
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71 | #include <iostream>
using namespace std;
int arr[1000000];
int heap_size;
template<typename T>
void _swap(T& a, T& b) {
T temp = a;
a = b;
b = temp;
}
inline int parent(int i) {
return (i - 1) >> 1;
}
inline int left(int i) {
return (i << 1) + 1;
}
inline int right(int i) {
return (i << 1) + 2;
}
void max_heapify(int i) {
int largest;
int l = left(i);
int r = right(i);
if (l < heap_size && arr[l] > arr[i]) {
largest = l;
} else {
largest = i;
}
if (r < heap_size && arr[r] > arr[largest])
largest = r;
if (largest != i) {
_swap(arr[largest], arr[i]);
max_heapify(largest);
}
}
void build_maxheap() {
for (int i = parent(heap_size-1); i >= 0; i--) {
max_heapify(i);
}
}
void heapsort() {
build_maxheap();
for (int i = (heap_size-1); i >= 0; i--) {
_swap(arr[i], arr[0]);
heap_size--; // reduce heap_size at here;
max_heapify(0);
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
int n = 5000;
//cin >> n;
heap_size = n;
for (int i = 0; i < n; i++) {
arr[i] = rand()%5000;
}
heapsort();
for (int i = 0; i < n; i++) {
cout << arr[i] << '\n';
}
return 0;
}
|
- Sort
