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Commit 8990522

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Add merge sort in es6
1 parent 28b93ad commit 8990522

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2 files changed

+172
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2 files changed

+172
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Lines changed: 105 additions & 0 deletions
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// sample of arrays to sort
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const arrayRandom = [9, 2, 5, 6, 4, 3, 7, 10, 1, 8];
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const arrayOrdered = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
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const arrayReversed = [10, 9, 8, 7, 6, 5, 4, 3, 2, 1];
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let countOuter = 0;
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let countInner = 0;
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let countSwap = 0;
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function resetCounters() {
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countOuter = 0;
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countInner = 0;
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countSwap = 0;
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}
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// top-down implementation
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function mergeSortTopDown(array) {
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countOuter++;
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if(array.length < 2) {
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return array;
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}
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const middle = Math.floor(array.length / 2);
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const left = array.slice(0, middle);
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const right = array.slice(middle);
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return mergeTopDown(mergeSortTopDown(left), mergeSortTopDown(right));
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}
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function mergeTopDown(left, right) {
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const array = [];
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while(left.length && right.length) {
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countInner++;
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if(left[0] < right[0]) {
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array.push(left.shift());
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} else {
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array.push(right.shift());
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}
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}
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return array.concat(left.slice()).concat(right.slice());
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}
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mergeSortTopDown(arrayRandom.slice()); // => outer: 19 inner: 24 swap: 0
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
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mergeSortTopDown(arrayOrdered.slice()); // => outer: 19 inner: 15 swap: 0
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
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mergeSortTopDown(arrayReversed.slice()); // => outer: 19 inner: 19 swap: 0
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
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// bottom-up implementation
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function mergeSortBottomUp(array) {
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let step = 1;
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while (step < array.length) {
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countOuter++;
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let left = 0;
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while (left + step < array.length) {
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countInner++;
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mergeBottomUp(array, left, step);
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left += step * 2;
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}
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step *= 2;
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}
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return array;
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}
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function mergeBottomUp(array, left, step) {
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const right = left + step;
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const end = Math.min(left + step * 2 - 1, array.length - 1);
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let leftMoving = left;
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let rightMoving = right;
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const temp = [];
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for (let i = left; i <= end; i++) {
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if ((array[leftMoving] <= array[rightMoving] || rightMoving > end) &&
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leftMoving < right) {
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temp[i] = array[leftMoving];
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leftMoving++;
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} else {
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temp[i] = array[rightMoving];
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rightMoving++;
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}
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}
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for (let j = left; j <= end; j++) {
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countSwap++;
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array[j] = temp[j];
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}
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}
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mergeSortBottomUp(arrayRandom.slice()); // => outer: 4 inner: 9 swap: 36
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
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mergeSortBottomUp(arrayOrdered.slice()); // => outer: 4 inner: 9 swap: 36
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
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mergeSortBottomUp(arrayReversed.slice()); // => outer: 4 inner: 9 swap: 36
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console.log('outer:', countOuter, 'inner:', countInner, 'swap:', countSwap);
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resetCounters();
Lines changed: 67 additions & 0 deletions
Original file line numberDiff line numberDiff line change
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// array to sort
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const array = [9, 2, 5, 6, 4, 3, 7, 10, 1, 8];
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// top-down implementation
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function mergeSortTopDown(array) {
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if(array.length < 2) {
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return array;
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}
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const middle = Math.floor(array.length / 2);
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const left = array.slice(0, middle);
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const right = array.slice(middle);
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return mergeTopDown(mergeSortTopDown(left), mergeSortTopDown(right));
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}
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function mergeTopDown(left, right) {
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const array = [];
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while(left.length && right.length) {
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if(left[0] < right[0]) {
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array.push(left.shift());
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} else {
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array.push(right.shift());
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}
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}
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return array.concat(left.slice()).concat(right.slice());
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}
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console.log(mergeSortTopDown(array.slice())); // => [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
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// bottom-up implementation
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function mergeSortBottomUp(array) {
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let step = 1;
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while (step < array.length) {
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let left = 0;
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while (left + step < array.length) {
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mergeBottomUp(array, left, step);
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left += step * 2;
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}
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step *= 2;
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}
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return array;
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}
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function mergeBottomUp(array, left, step) {
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const right = left + step;
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const end = Math.min(left + step * 2 - 1, array.length - 1);
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let leftMoving = left;
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let rightMoving = right;
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const temp = [];
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for (let i = left; i <= end; i++) {
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if ((array[leftMoving] <= array[rightMoving] || rightMoving > end) &&
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leftMoving < right) {
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temp[i] = array[leftMoving];
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leftMoving++;
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} else {
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temp[i] = array[rightMoving];
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rightMoving++;
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}
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}
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for (let j = left; j <= end; j++) {
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array[j] = temp[j];
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}
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}
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console.log(mergeSortBottomUp(array.slice())); // => [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]

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