Merge pull request #128 from 24apurv/heap-sort-java

Heap sort for java added

Java/HeapSort.java

@@ -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));
+    }
+}