Added Heap Sort in Java and updated README.md about adding Heap Sort …

…for Java (#577)

README.md

@@ -175,7 +175,7 @@ The community maintained a list of **Algorithms and Data Structures** implementa
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algorithms/ar-hsrt/java/HeapSort.java

@@ -0,0 +1,56 @@
+public class HeapSort {
+
+    public void sort(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_element = arr[0];
+            arr[0] = arr[i];
+            arr[i] = temp_element;
+
+            heapify(arr, i, 0);
+        }
+    }
+
+    public 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);
+        }
+    }
+
+    public static void main(String args[]){
+        int input[] = {15, 2, 8, 9, 0, 1, 12, 22};
+        int n = input.length;
+
+        HeapSort ob = new HeapSort();
+        ob.sort(input);
+
+        System.out.println("Sorted array is");
+
+        for (int i=0; i<n; ++i) {
+            System.out.print(input[i] + " ");
+        }
+    }
+}