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Commit 87a4693

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implemented heap sort
1 parent d647668 commit 87a4693

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2 files changed

+72
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‎src/sorting/heap.js‎

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// To heapify a subtree rooted with node 'index' which is
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// an index in arr[]. 'size' is size of heap
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const heapify = (arr, size, index) => {
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let largest = index; // Initialize largest as root
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const left = 2 * index + 1;
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const right = 2 * index + 2;
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// If left child is larger than root
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if (left < size && arr[left] > arr[largest]) {
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largest = left;
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}
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// If right child is larger than root
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if (right < size && arr[right] > arr[largest]) {
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largest = right;
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}
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// If largest is not root
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if (largest !== index) {
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// swap values
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[arr[index], arr[largest]] = [arr[largest], arr[index]];
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// Recursively heapify the affected sub-tree
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heapify(arr, size, largest);
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}
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};
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const heapSort = (arr) => {
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// No need to sort the array if the array only has one element or empty
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if (arr.length < 2) return arr;
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const result = arr.slice(0);
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// Build heap (rearrange array) for first time
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for (let i = Math.floor(result.length / 2 - 1); i >= 0; i -= 1) {
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heapify(result, result.length, i);
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}
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// One by one extract an element from heap and again rearrange
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for (let i = result.length - 1; i >= 0; i -= 1) {
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// Move current root to end
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[result[0], result[i]] = [result[i], result[0]];
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// call max heapify on the reduced heap
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heapify(result, i, 0);
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}
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return result;
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};
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module.exports = heapSort;

‎tests/sorting/heap.test.js‎

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const heapSort = require('../../src/sorting/heap');
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describe('heap sort unit test:', () => {
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it('Test#1 simple', async () => {
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const want = [2, 3, 5, 6, 7, 9];
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const got = heapSort([5, 3, 7, 6, 2, 9]);
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expect(got).toEqual(want);
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});
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it('Test#2 duplicate value', async () => {
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const want = [2, 3, 5, 5, 6, 7, 7, 9];
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const got = heapSort([5, 3, 7, 6, 2, 9, 7, 5]);
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expect(got).toEqual(want);
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});
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it('Test#3 with negative value', async () => {
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const want = [-7, -7, -3, 6, 17, 34, 42, 50, 52, 83, 87, 89, 96];
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const got = heapSort([83, 52, 89, 42, 6, 87, 50, 17, 34, 96, -7, -3, -7]);
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expect(got).toEqual(want);
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});
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});

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