feat(heap): add error handling for heaps

BREAKING CHANGE: size is now an attribute rather than a method. Similar to the built-in Map.size and Set.size

Author: amejiarosario

src/data-structures/heaps/heap.js

@@ -8,7 +8,11 @@
 classHeap{
 constructor(comparator=(a,b)=>a-b){
 this.array=[];
-this.comparator=(i1,i2)=>comparator(this.array[i1],this.array[i2]);
+this.comparator=(i1,i2)=>{
+constvalue=comparator(this.array[i1],this.array[i2]);
+if(Number.isNaN(value)){thrownewError(`Comparator should evaluate to a number. Got ${value} when comparing ${this.array[i1]} with ${this.array[i2]}`);}
+returnvalue;
+};
 }
 
 /**
@@ -34,8 +38,8 @@ class Heap {
  * @runtime O(log n)
  */
 remove(index=0){
-if(!this.size())returnnull;
-this.swap(index,this.size()-1);// swap with last
+if(!this.size)returnnull;
+this.swap(index,this.size-1);// swap with last
 constvalue=this.array.pop();// remove element
 this.bubbleDown(index);
 returnvalue;
@@ -45,7 +49,7 @@ class Heap {
  * Returns the number of elements in this collection.
  * @runtime O(1)
  */
-size(){
+getsize(){
 returnthis.array.length;
 }
 
@@ -54,7 +58,7 @@ class Heap {
  * @runtime O(log n)
  */
 bubbleUp(){
-letindex=this.size()-1;
+letindex=this.size-1;
 constparent=(i)=>Math.ceil(i/2-1);
 while(parent(index)>=0&&this.comparator(parent(index),index)>0){
 this.swap(parent(index),index);
@@ -70,18 +74,18 @@ class Heap {
 letcurr=index;
 constleft=(i)=>2*i+1;
 constright=(i)=>2*i+2;
-constgetTopChild=(i)=>(right(i)<this.size()
+constgetTopChild=(i)=>(right(i)<this.size
 &&this.comparator(left(i),right(i))>0 ? right(i) : left(i));
 
-while(left(curr)<this.size()&&this.comparator(curr,getTopChild(curr))>0){
+while(left(curr)<this.size&&this.comparator(curr,getTopChild(curr))>0){
 constnext=getTopChild(curr);
 this.swap(curr,next);
 curr=next;
 }
 }
 
 /**
- * "Private": Swap elements on the heap
+ * Swap elements on the heap
  * @runtime O(1)
  * @param {number} i1 index 1
  * @param {number} i2 index 2

src/data-structures/heaps/heap.spec.js

@@ -3,12 +3,16 @@ const PriorityQueue = require('./priority-queue');
 constMaxHeap=require('./max-heap');
 constMinHeap=require('./min-heap');
 
-[[Heap],[PriorityQueue],[MinHeap]].forEach(([DS,arg])=>{
-describe('Min-Heap (Priority Queue)',()=>{
+[
+[Heap],
+[PriorityQueue,[],(a,b)=>a-b],
+[MinHeap],
+].forEach(([DS, ...arg])=>{
+describe('Min-Heap and Priority Queue',()=>{
 letheap;
 
 beforeEach(()=>{
-heap=newDS(arg);
+heap=newDS(...arg);
 });
 
 describe('#contructor',()=>{
@@ -21,7 +25,7 @@ const MinHeap = require('./min-heap');
 it('should add an element',()=>{
 expect(heap.add(1)).toBe(undefined);
 expect(heap.array).toEqual([1]);
-expect(heap.size()).toBe(1);
+expect(heap.size).toBe(1);
 });
 
 it('should keep things in order',()=>{
@@ -31,7 +35,7 @@ const MinHeap = require('./min-heap');
 expect(heap.array[0]).toEqual(2);
 heap.add(1);
 expect(heap.array[0]).toEqual(1);
-expect(heap.size()).toEqual(3);
+expect(heap.size).toEqual(3);
 });
 });
 
@@ -40,7 +44,7 @@ const MinHeap = require('./min-heap');
 heap.add(1);
 heap.add(0);
 expect(heap.remove()).toBe(0);
-expect(heap.size()).toBe(1);
+expect(heap.size).toBe(1);
 expect(heap.array).toEqual([1]);
 });
 
@@ -70,19 +74,23 @@ const MinHeap = require('./min-heap');
 expect(heap.remove()).toEqual(1);
 expect(heap.remove()).toEqual(2);
 expect(heap.remove()).toEqual(3);
-expect(heap.size()).toBe(0);
+expect(heap.size).toBe(0);
 });
 });
 });
 });
 });
 
-[[Heap,(a,b)=>b-a],[PriorityQueue,(a,b)=>b-a],[MaxHeap]].forEach(([DS,arg])=>{
+[
+[Heap,(a,b)=>b-a],
+[PriorityQueue,[],(a,b)=>b-a],
+[MaxHeap],
+].forEach(([DS, ...arg])=>{
 describe('Max-Heap (Priority Queue)',()=>{
 letheap;
 
 beforeEach(()=>{
-heap=newDS(arg);
+heap=newDS(...arg);
 });
 
 describe('#contructor',()=>{
@@ -95,7 +103,7 @@ const MinHeap = require('./min-heap');
 it('should add an element',()=>{
 expect(heap.add(1)).toBe(undefined);
 expect(heap.array).toEqual([1]);
-expect(heap.size()).toBe(1);
+expect(heap.size).toBe(1);
 });
 
 it('should keep things in order',()=>{
@@ -105,7 +113,7 @@ const MinHeap = require('./min-heap');
 expect(heap.array[0]).toEqual(2);
 heap.add(3);
 expect(heap.array[0]).toEqual(3);
-expect(heap.size()).toEqual(3);
+expect(heap.size).toEqual(3);
 });
 });
 
@@ -114,7 +122,7 @@ const MinHeap = require('./min-heap');
 heap.add(1);
 heap.add(0);
 expect(heap.remove()).toBe(1);
-expect(heap.size()).toBe(1);
+expect(heap.size).toBe(1);
 expect(heap.array).toEqual([0]);
 });
 
@@ -156,7 +164,7 @@ const MinHeap = require('./min-heap');
 expect(heap.remove()).toEqual(2);
 expect(heap.remove()).toEqual(1);
 expect(heap.remove()).toEqual(0);
-expect(heap.size()).toBe(0);
+expect(heap.size).toBe(0);
 });
 });
 });

src/data-structures/heaps/median-heap.js

@@ -30,9 +30,9 @@ class MedianHeap {
 }
 
 // rebalance if the sizes of the heaps differ by more than one element
-if(Math.abs(this.min.size()-this.max.size())>1){
+if(Math.abs(this.min.size-this.max.size)>1){
 // extract the min/max from the heap with more elements and insert it into the other heap.
-if(this.min.size()>this.max.size()){
+if(this.min.size>this.max.size){
 this.max.add(this.min.remove());
 }else{
 this.min.add(this.max.remove());
@@ -47,12 +47,12 @@ class MedianHeap {
 findMedian(){
 letmedian;
 
-if(this.max.size()===this.min.size()){
+if(this.max.size===this.min.size){
 // When both heaps contain the same number of elements,
 // the total number of elements is even.
 // The median is the mean of the two middle elements.
 median=(this.max.peek()+this.min.peek())/2;
-}elseif(this.max.size()>this.min.size()){
+}elseif(this.max.size>this.min.size){
 // when the max-heap contains one more element than the min-heap,
 // the median is in the top of the max-heap.
 median=this.max.peek();
@@ -67,8 +67,8 @@ class MedianHeap {
 /**
  * Return size of the heap.
  */
-size(){
-returnthis.min.size()+this.max.size();
+getsize(){
+returnthis.min.size+this.max.size;
 }
 }
 

src/data-structures/heaps/median-heap.spec.js

@@ -10,13 +10,13 @@ describe('Median Heap', () => {
 describe('#add',()=>{
 it('should work',()=>{
 expect(medianHeap.add(1)).toEqual(undefined);
-expect(medianHeap.size()).toEqual(1);
+expect(medianHeap.size).toEqual(1);
 });
 
 it('should work',()=>{
 expect(medianHeap.add(1)).toEqual(undefined);
 expect(medianHeap.add(1)).toEqual(undefined);
-expect(medianHeap.size()).toEqual(2);
+expect(medianHeap.size).toEqual(2);
 });
 });