89 lines
2.1 KiB
JavaScript
89 lines
2.1 KiB
JavaScript
/**
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* Efficient sort implementations.
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*
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* Note: These sort implementations were created to compare different sorting algorithms in JavaScript.
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* Don't use them if you don't know what you are doing. Native Array.sort is almost always a better choice.
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*
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* @module sort
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*/
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import * as math from './math.js'
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/**
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* @template T
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* @param {Array<T>} arr
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* @param {number} lo
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* @param {number} hi
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* @param {function(T,T):number} compare
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*/
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export const _insertionSort = (arr, lo, hi, compare) => {
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for (let i = lo + 1; i <= hi; i++) {
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for (let j = i; j > 0 && compare(arr[j - 1], arr[j]) > 0; j--) {
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const tmp = arr[j]
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arr[j] = arr[j - 1]
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arr[j - 1] = tmp
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}
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}
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}
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/**
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* @template T
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* @param {Array<T>} arr
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* @param {function(T,T):number} compare
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* @return {void}
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*/
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export const insertionSort = (arr, compare) => {
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_insertionSort(arr, 0, arr.length - 1, compare)
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}
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/**
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* @template T
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* @param {Array<T>} arr
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* @param {number} lo
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* @param {number} hi
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* @param {function(T,T):number} compare
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*/
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const _quickSort = (arr, lo, hi, compare) => {
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if (hi - lo < 42) {
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_insertionSort(arr, lo, hi, compare)
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} else {
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const pivot = arr[math.floor((lo + hi) / 2)]
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let i = lo
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let j = hi
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while (true) {
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while (compare(pivot, arr[i]) > 0) {
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i++
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}
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while (compare(arr[j], pivot) > 0) {
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j--
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}
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if (i >= j) {
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break
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}
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// swap arr[i] with arr[j]
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// and increment i and j
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const arri = arr[i]
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arr[i++] = arr[j]
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arr[j--] = arri
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}
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_quickSort(arr, lo, j, compare)
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_quickSort(arr, j + 1, hi, compare)
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}
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}
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/**
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* This algorithm beats Array.prototype.sort in Chrome only with arrays with 10 million entries.
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* In most cases [].sort will do just fine. Make sure to performance test your use-case before you
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* integrate this algorithm.
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*
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* Note that Chrome's sort is now a stable algorithm (Timsort). Quicksort is not stable.
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*
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* @template T
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* @param {Array<T>} arr
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* @param {function(T,T):number} compare
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* @return {void}
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*/
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export const quicksort = (arr, compare) => {
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_quickSort(arr, 0, arr.length - 1, compare)
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}
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