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heap.cpp
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heap.cpp
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// C++ program for implementation of Heap Sort
#include <iostream>
using namespace std;
// To heapify a subtree rooted with node i
// which is an index in arr[].
// n is size of heap
void heapify(int arr[], int N, int i) {
// Initialize largest as root
int largest = i;
// left = 2*i + 1
int l = 2 * i + 1;
// right = 2*i + 2
int r = 2 * i + 2;
// If left child is larger than root
if (l < N && arr[l] > arr[largest])
largest = l;
// If right child is larger than largest
// so far
if (r < N && arr[r] > arr[largest])
largest = r;
// If largest is not root
if (largest != i) {
swap(arr[i], arr[largest]);
// Recursively heapify the affected
// sub-tree
heapify(arr, N, largest);
}
}
// Main function to do heap sort
void heapSort(int arr[], int N) {
// Build heap (rearrange array)
for (int i = N / 2 - 1; i >= 0; i--)
heapify(arr, N, i);
// One by one extract an element
// from heap
for (int i = N - 1; i > 0; i--) {
// Move current root to end
swap(arr[0], arr[i]);
// call max heapify on the reduced heap
heapify(arr, i, 0);
}
}
// A utility function to print array of size n
void printArray(int arr[], int N) {
for (int i = 0; i < N; ++i)
cout << arr[i] << " ";
cout << "\n";
}
// Driver's code
int main() {
int arr[] = { 12, 11, 13, 5, 6, 7 };
int N = sizeof(arr) / sizeof(arr[0]);
// Function call
heapSort(arr, N);
cout << "Sorted array is \n";
printArray(arr, N);
}