diff --git a/05-labHeapSort/Assignment.java b/05-labHeapSort/Assignment.java
index 13af5ec..cc28b5c 100644
--- a/05-labHeapSort/Assignment.java
+++ b/05-labHeapSort/Assignment.java
@@ -4,20 +4,43 @@ import java.io.*;
 import java.util.*;
 
 public class Assignment {
-
     public static int[] heapify(int[] heap, int sizeA, int index) {
-        // Fill in here
+        // check parent and children to find the largest node
+        int largest = index;
+        int left = 2 * index + 1;
+        int right = 2 * index + 2;
+
+        if (left < sizeA && heap[left] > heap[largest]) largest = left;
+        if (right < sizeA && heap[right] > heap[largest]) largest = right;
+
+        // if largest isn't the parent, swap with the largest child and recursively heapify
+        if (largest != index) {
+            final int tmp = heap[index];
+            heap[index] = heap[largest];
+            heap[largest] = tmp;
+            return heapify(heap, sizeA, largest);
+        }
         return heap;
     }
 
     public static int[] buildHeap(int[] arr, int sizeA) {
-        // Fill in here
-        return heapify(arr, sizeA, 1);
+        for (int i = sizeA / 2; i > 0; i--) {
+            heapify(arr, sizeA, i);
+        }
+        return heapify(arr, sizeA, 0);
     }
 
     public static int[] heapSort(int[] arr, int sizeA) {
-        // Fill in here
-        return buildHeap(arr, sizeA);
+        arr = buildHeap(arr, sizeA);
+        // for each element
+        for (int i = 1; i < sizeA; i++) {
+            // swap heap top (largest element) with the last array element and reheapify
+            int top = arr[0];
+            arr[0] = arr[sizeA - i];
+            arr[sizeA - i] = top;
+            arr = heapify(arr, sizeA - i, 0);
+        }
+        return arr;
     }
 
     public static void run(String inputPath) {