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src/data-structures/heap/MinHeap.js

@@ -126,6 +126,8 @@ export default class MinHeap {
       return 0;
     }
 
+    // Min heap may be converted to max heap by simply changing this line to:
+    // a > b ? -1 : 1
     return a < b ? -1 : 1;
   }
 

src/data-structures/heap/__test__/MinHeap.test.js

@@ -26,6 +26,19 @@ describe('MinHeap', () => {
     minHeap.add(1);
     expect(minHeap.peek()).toBe(1);
     expect(minHeap.toString()).toBe('1,3,10,5');
+
+    minHeap.add(1);
+    expect(minHeap.peek()).toBe(1);
+    expect(minHeap.toString()).toBe('1,1,10,5,3');
+
+    expect(minHeap.poll()).toBe(1);
+    expect(minHeap.toString()).toBe('1,3,10,5');
+
+    expect(minHeap.poll()).toBe(1);
+    expect(minHeap.toString()).toBe('3,5,10');
+
+    expect(minHeap.poll()).toBe(3);
+    expect(minHeap.toString()).toBe('5,10');
   });
 
   it('should poll items from the heap and heapify it down', () => {
@@ -57,4 +70,20 @@ describe('MinHeap', () => {
     expect(minHeap.poll()).toBeNull();
     expect(minHeap.toString()).toBe('');
   });
+
+  it('should heapify down through the right branch as well', () => {
+    const minHeap = new MinHeap();
+
+    minHeap.add(3);
+    minHeap.add(12);
+    minHeap.add(10);
+
+    expect(minHeap.toString()).toBe('3,12,10');
+
+    minHeap.add(11);
+    expect(minHeap.toString()).toBe('3,11,10,12');
+
+    expect(minHeap.poll()).toBe(3);
+    expect(minHeap.toString()).toBe('10,11,12');
+  });
 });