Merge pull request #227 from aarxshi/main

Add Heap Sort implementation in Java

Author: Pradeepsingh61

Java/algorithms/sorting/HeapSort_Aarushi.java

@@ -0,0 +1,72 @@
+/**
+ * Algorithm: Heap Sort
+ * Description: Implementation of Heap Sort algorithm using binary heap
+ * Time Complexity: O(n log n) for all cases
+ * Space Complexity: O(1) (in-place)
+ */
+import java.util.Scanner;
+public class HeapSort {
+
+    public static int[] arrInput(Scanner sc) {
+        System.out.print("Enter the size of the array: ");
+        int n = sc.nextInt();
+        int[] arr = new int[n];
+        System.out.println("Enter the elements of the array: ");
+        for (int i = 0; i < n; i++) {
+            arr[i] = sc.nextInt();
+        }
+        return arr;
+    }
+
+    public static void heapSort(int[] arr) {
+        int n = arr.length;
+        // Build max heap
+        for (int i = n / 2 - 1; i >= 0; i--) {
+            heapify(arr, n, i);
+        }
+        // Extract elements from heap
+        for (int i = n - 1; i >= 0; i--) {
+            // Swap current root with end
+            int temp = arr[0];
+            arr[0] = arr[i];
+            arr[i] = temp;
+            // Heapify reduced heap
+            heapify(arr, i, 0);
+        }
+    }
+
+    public static void heapify(int[] arr, int n, int i) {
+        int largest = i;  
+        int left = 2 * i + 1;  
+        int right = 2 * i + 2;  
+        if (left < n && arr[left] > arr[largest]) {
+            largest = left;
+        }
+        if (right < n && arr[right] > arr[largest]) {
+            largest = right;
+        }
+        if (largest != i) {
+            int swap = arr[i];
+            arr[i] = arr[largest];
+            arr[largest] = swap;
+            heapify(arr, n, largest);
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int[] arr = arrInput(sc);
+        System.out.print("Array before sorting: ");
+        for (int num : arr) {
+            System.out.print(num + " ");
+        }
+        System.out.println();
+        heapSort(arr);
+        System.out.print("Array after sorting: ");
+        for (int num : arr) {
+            System.out.print(num + " ");
+        }
+        System.out.println();
+        sc.close();
+    }
+}