2021-10-07 09:03:38 +02:00
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/*
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* MergeSort implementation.
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*
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* Merge Sort is an algorithm where the main list is divided down into two half sized lists, which then have merge sort
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* called on these two smaller lists recursively until there is only a sorted list of one.
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2020-05-03 09:05:12 +02:00
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*
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2017-10-04 20:20:23 -04:00
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* On the way up the recursive calls, the lists will be merged together inserting
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* the smaller value first, creating a larger sorted list.
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*/
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/**
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2021-10-07 09:03:38 +02:00
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* Sort and merge two given arrays.
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*
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* @param {Array} list1 Sublist to break down.
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* @param {Array} list2 Sublist to break down.
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* @return {Array} The merged list.
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2017-10-04 20:20:23 -04:00
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*/
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2021-10-07 09:03:38 +02:00
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export function merge (list1, list2) {
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2021-05-05 12:24:42 +03:00
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const results = []
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let i = 0
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let j = 0
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2017-10-04 20:20:23 -04:00
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2021-05-05 12:24:42 +03:00
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while (i < list1.length && j < list2.length) {
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if (list1[i] < list2[j]) {
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results.push(list1[i++])
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2017-10-04 20:20:23 -04:00
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} else {
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2021-05-05 12:24:42 +03:00
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results.push(list2[j++])
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2017-10-04 20:20:23 -04:00
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}
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}
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2021-05-05 12:24:42 +03:00
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return results.concat(list1.slice(i), list2.slice(j))
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2017-10-04 20:20:23 -04:00
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}
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/**
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2021-10-07 09:03:38 +02:00
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* Break down the lists into smaller pieces to be merged.
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*
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* @param {Array} list List to be sorted.
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* @return {Array} The sorted list.
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2017-10-04 20:20:23 -04:00
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*/
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2021-10-07 09:03:38 +02:00
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export function mergeSort (list) {
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2020-05-03 09:05:12 +02:00
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if (list.length < 2) return list
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2017-10-04 20:20:23 -04:00
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2021-05-22 14:41:53 +03:00
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const listHalf = Math.floor(list.length / 2)
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const subList1 = list.slice(0, listHalf)
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const subList2 = list.slice(listHalf, list.length)
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2017-10-04 20:20:23 -04:00
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2020-05-03 09:05:12 +02:00
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return merge(mergeSort(subList1), mergeSort(subList2))
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2017-10-04 20:20:23 -04:00
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}
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