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Heap sort for java added #128

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Oct 5, 2020
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62 changes: 62 additions & 0 deletions Java/HeapSort.java
Original file line number Diff line number Diff line change
@@ -0,0 +1,62 @@
import java.util.Arrays;
import java.util.Scanner;

public class HeapSort {

/**
* Java method to heapify subtree with root node i
*
* @param int[] arr : array
* @param int n : size of heap
* @param int i : node
*/
public static void heapify(int arr[], int n, int i) {
int largest = i;
int l = 2 * i + 1;
int r = 2 * i + 2;
if (l < n && arr[l] > arr[largest])
largest = l;
if (r < n && arr[r] > arr[largest])
largest = r;
if (largest != i) {
int swap = arr[i];
arr[i] = arr[largest];
arr[largest] = swap;
heapify(arr, n, largest);
}
}

/**
* Java method to sort array using heap sort
*
* @param int[] arr : array
*/
public static void heapSort(int arr[]) {
int n = arr.length;
for (int i = n / 2 - 1; i >= 0; i--)
heapify(arr, n, i);
for (int i = n - 1; i > 0; i--) {
int temp = arr[0];
arr[0] = arr[i];
arr[i] = temp;
heapify(arr, i, 0);
}
}

public static void main(String[] args) {
Scanner sc = new Scanner(System.in);

int n;
System.out.println("Enter the number of array elements: ");
n = sc.nextInt();

int arr[] = new int[n];
System.out.println("Enter the array elements: ");
for (int i = 0; i < n; i++)
arr[i] = sc.nextInt();

System.out.println("Original array : " + Arrays.toString(arr));
heapSort(arr);
System.out.println("Sorted array : " + Arrays.toString(arr));
}
}