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Heaps #156
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Heaps #156
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15e262f
update: entry in TOC.md
ashokdey c2f5934
fix: used pop() instead of splice()
ashokdey 5338710
update: added MinHeap, support for collection in constructor
ashokdey 16006e0
fix: order of length check in remove()
ashokdey 7b958e9
fix & update: handled case of min/max element 0, fixes in tests
ashokdey 6ced3ff
update: entry in TOC.md
ashokdey 042670a
update: added k smallest elements problem
ashokdey f9f2cfc
update: added K largest array elements
ashokdey a03369c
fix: repo name change
ashokdey 875f6ca
fix: repo placement
ashokdey 4f5f695
cleanup
ashokdey 1e2a548
update: entry in TOC.md
ashokdey c2d8c12
fix: remove will return and remove the element from the heap
ashokdey c3e44df
update: README makeover
ashokdey 2daa87d
fixes: README changes
ashokdey 2c1011a
update: Added links in README
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59 changes: 59 additions & 0 deletions
src/_DataStructures_/Heaps/MinHeap/MinHeap.test.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,59 @@ | ||
| const MinHeap = require('.'); | ||
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| describe('MinHeap', () => { | ||
| it('Should be a class', () => { | ||
| expect(typeof MinHeap.prototype.constructor).toEqual('function'); | ||
| }); | ||
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| const mh = new MinHeap(); | ||
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| beforeEach(() => { | ||
| mh.destroy(); | ||
| }); | ||
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| it('Should create an instance of MinHeap', () => { | ||
| expect(mh instanceof MinHeap).toEqual(true); | ||
| }); | ||
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| it('Should create a MinHeap using collection', () => { | ||
| const mHBulk = new MinHeap([112, 3, 21, 9, 10, 0]); | ||
| expect(mHBulk.getMin()).toEqual(0); | ||
| }); | ||
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| it('Should add an element to the MinHeap', () => { | ||
| mh.add(10); | ||
| expect(mh.getMin()).toEqual(10); | ||
| }); | ||
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| it('Should keep the smallest element at the root', () => { | ||
| [12, 5, 34].forEach(el => mh.add(el)); | ||
| expect(mh.getMin()).toEqual(5); | ||
| }); | ||
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| it('Should retain Heap properties after removal of an element', () => { | ||
| [12, 45, 1, 34].forEach(el => mh.add(el)); | ||
| expect(mh.getMin()).toEqual(1); | ||
| mh.remove(); | ||
| expect(mh.getMin()).toEqual(12); | ||
| }); | ||
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| it('Should return `null` when heap is empty', () => { | ||
| [1, 34].forEach(el => mh.add(el)); | ||
| expect(mh.getMin()).toEqual(1); | ||
| mh.remove(); | ||
| mh.remove(); | ||
| expect(mh.getMin()).toEqual(null); | ||
| }); | ||
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| it('Should return the elelment value on `remove()`', () => { | ||
| [1, 34].forEach(el => mh.add(el)); | ||
| expect(mh.getMin()).toEqual(1); | ||
| expect(mh.remove()).toEqual(1); | ||
| expect(mh.remove()).toEqual(34); | ||
| expect(mh.getMin()).toEqual(null); | ||
| }); | ||
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| it('Should return `null` on `remove() called on empty heap`', () => { | ||
| expect(mh.getMin()).toEqual(null); | ||
| }); | ||
| }); |
78 changes: 78 additions & 0 deletions
src/_DataStructures_/Heaps/MinHeap/index.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,78 @@ | ||
| class MinHeap { | ||
| constructor(collection) { | ||
| this.heap = []; | ||
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| if (collection) { | ||
| collection.forEach((element) => { | ||
| this.add(element); | ||
| }); | ||
| } | ||
| } | ||
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| add(element) { | ||
| this.heap.push(element); | ||
| // check for the parent element & swap if required | ||
| // eslint-disable-next-line no-underscore-dangle | ||
| this.__traverseUpAndSwap(this.heap.length - 1); | ||
| } | ||
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| getMin() { | ||
| return this.heap[0] !== undefined ? this.heap[0] : null; | ||
| } | ||
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| remove() { | ||
| const min = this.heap[0] !== undefined ? this.heap[0] : null; | ||
| if (this.heap.length === 1) { | ||
| this.heap.pop(); | ||
| } | ||
| if (this.heap.length > 1) { | ||
| this.heap[0] = this.heap[this.heap.length - 1]; | ||
| this.heap.pop(); | ||
| // eslint-disable-next-line no-underscore-dangle | ||
| this.__heapify(0); | ||
| } | ||
| return min; | ||
| } | ||
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| destroy() { | ||
| this.heap = []; | ||
| } | ||
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| // eslint-disable-next-line consistent-return | ||
| __traverseUpAndSwap(index) { | ||
| if (index <= 0) return null; | ||
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| const parent = Math.floor(index / 2); | ||
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| if (this.heap[parent] > this.heap[index]) { | ||
| const temp = this.heap[parent]; | ||
| this.heap[parent] = this.heap[index]; | ||
| this.heap[index] = temp; | ||
| // eslint-disable-next-line no-underscore-dangle | ||
| this.__traverseUpAndSwap(parent); | ||
| } | ||
| } | ||
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| __heapify(index) { | ||
| const left = index * 2; | ||
| const right = index * 2 + 1; | ||
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| let smallest = index; | ||
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| if (this.heap.length > left && this.heap[smallest] > this.heap[left]) { | ||
| smallest = left; | ||
| } | ||
| if (this.heap.length > right && this.heap[smallest] > this.heap[right]) { | ||
| smallest = right; | ||
| } | ||
| if (smallest !== index) { | ||
| const tmp = this.heap[smallest]; | ||
| this.heap[smallest] = this.heap[index]; | ||
| this.heap[index] = tmp; | ||
| // eslint-disable-next-line no-underscore-dangle | ||
| this.__heapify(smallest); | ||
| } | ||
| } | ||
| } | ||
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| module.exports = MinHeap; |
22 changes: 22 additions & 0 deletions
src/_DataStructures_/Heaps/k-largest-in-array/index.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| const MaxHeap = require('../MaxHeap'); | ||
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| /** | ||
| * Find the 4 largest elements from an array | ||
| */ | ||
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| function findKLargest(collection, k) { | ||
| if (!collection || !Array.isArray(collection)) { | ||
| throw new Error('Invalid / missing collection'); | ||
| } | ||
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| // create a MaxHeap using the collection | ||
| const mh = new MaxHeap(collection); | ||
| const result = []; | ||
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| for (let i = 0; i < k; i += 1) { | ||
| result.push(mh.remove()); | ||
| } | ||
| return result; | ||
| } | ||
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| module.exports = findKLargest; |
21 changes: 21 additions & 0 deletions
src/_DataStructures_/Heaps/k-smallest-in-array/index.js
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,21 @@ | ||
| /** | ||
| * Find 4 smallest elements in an array | ||
| */ | ||
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| const MinHeap = require('../MinHeap'); | ||
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| function findKSmallest(collection, k) { | ||
| if (!collection || !Array.isArray(collection)) { | ||
| throw new Error('Invalid / missing collection'); | ||
| } | ||
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| // create a MinHeap using the collection | ||
| const mh = new MinHeap(collection); | ||
| const result = []; | ||
| for (let i = 0; i < k; i += 1) { | ||
| result.push(mh.remove()); | ||
| } | ||
| return result; | ||
| } | ||
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| module.exports = findKSmallest; |
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