Fixed a bug in the getHeadValue of the Heap structures

Author: phishman3579

src/com/jwetherell/algorithms/data_structures/BinaryHeap.java

@@ -341,7 +341,7 @@ public T[] getHeap() {
          */
         @Override
         public T getHeadValue() {
-            if (array.length == 0) return null;
+            if (size == 0 || array.length == 0) return null;
             return array[0];
         }
 

test/com/jwetherell/algorithms/data_structures/test/BinaryHeapTests.java

@@ -1,6 +1,7 @@
 package com.jwetherell.algorithms.data_structures.test;
 
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertNull;
 
 import java.util.Collection;
 
@@ -16,7 +17,7 @@ public class BinaryHeapTests {
 
     @Test
     public void testMinHeap() {
-        TestData data = Utils.generateTestData(100);
+        TestData data = Utils.generateTestData(2500);
 
         String aNameMin = "Min-Heap [array]";
         BinaryHeap.BinaryHeapArray<Integer> aHeapMin = new BinaryHeap.BinaryHeapArray<Integer>(BinaryHeap.Type.MIN);
@@ -26,18 +27,31 @@ public void testMinHeap() {
         assertTrue(JavaCollectionTest.testCollection(aCollectionMin, Integer.class, aNameMin,
                                                      data.unsorted, data.sorted, data.invalid));
 
+        BinaryHeap.BinaryHeapArray<Integer> aHeapNull = new BinaryHeap.BinaryHeapArray<Integer>(BinaryHeap.Type.MIN);
+        aHeapNull.add(10);
+        aHeapNull.add(11);
+        aHeapNull.clear();
+        assertNull(aHeapNull.getHeadValue()); // we expect null here
+
         String tNameMin = "Min-Heap [tree]";
         BinaryHeap.BinaryHeapTree<Integer> tHeapMin = new BinaryHeap.BinaryHeapTree<Integer>(BinaryHeap.Type.MIN);
         Collection<Integer> tCollectionMin = tHeapMin.toCollection();
         assertTrue(HeapTest.testHeap(BinaryHeap.Type.MIN, tHeapMin, Integer.class, tNameMin,
                                      data.unsorted, data.sorted, data.invalid));
         assertTrue(JavaCollectionTest.testCollection(tCollectionMin, Integer.class, tNameMin,
                                                      data.unsorted, data.sorted, data.invalid));
+
+        BinaryHeap.BinaryHeapTree<Integer> tHeapNull = new BinaryHeap.BinaryHeapTree<Integer>(BinaryHeap.Type.MIN);
+        tHeapNull.add(10);
+        tHeapNull.add(11);
+        tHeapNull.clear();
+        assertNull(tHeapNull.getHeadValue()); // we expect null here
+
     }
 
     @Test
     public void testMaxHeap() {
-        TestData data = Utils.generateTestData(1000);
+        TestData data = Utils.generateTestData(2500);
 
         String aNameMax = "Max-Heap [array]";
         BinaryHeap.BinaryHeapArray<Integer> aHeapMax = new BinaryHeap.BinaryHeapArray<Integer>(BinaryHeap.Type.MAX);
@@ -47,12 +61,24 @@ public void testMaxHeap() {
         assertTrue(JavaCollectionTest.testCollection(aCollectionMax, Integer.class, aNameMax,
                                                  data.unsorted, data.sorted, data.invalid));
 
+        BinaryHeap.BinaryHeapArray<Integer> aHeapNull = new BinaryHeap.BinaryHeapArray<Integer>(BinaryHeap.Type.MAX);
+        aHeapNull.add(10);
+        aHeapNull.add(11);
+        aHeapNull.clear();
+        assertNull(aHeapNull.getHeadValue()); // we expect null here
+
         String lNameMax = "Max-Heap [tree]";
         BinaryHeap.BinaryHeapTree<Integer> tHeapMax = new BinaryHeap.BinaryHeapTree<Integer>(BinaryHeap.Type.MAX);
         Collection<Integer> tCollectionMax = tHeapMax.toCollection();
         assertTrue(HeapTest.testHeap(BinaryHeap.Type.MAX, tHeapMax, Integer.class, lNameMax, 
                                      data.unsorted, data.sorted, data.invalid));
         assertTrue(JavaCollectionTest.testCollection(tCollectionMax, Integer.class, lNameMax,
                                                  data.unsorted, data.sorted, data.invalid));
+
+        BinaryHeap.BinaryHeapTree<Integer> tHeapNull = new BinaryHeap.BinaryHeapTree<Integer>(BinaryHeap.Type.MAX);
+        tHeapNull.add(10);
+        tHeapNull.add(11);
+        tHeapNull.clear();
+        assertNull(tHeapNull.getHeadValue()); // we expect null here
     }
 }