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6c2f83b752
* Add doctest for QuickSort * Add doctest for MergeSort Co-authored-by: Sukhpreet Sekhon <ssekhon@atb.com>
70 lines
1.7 KiB
JavaScript
70 lines
1.7 KiB
JavaScript
/**
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* Merge Sort is an algorithm where the main list is divided down into two half
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* sized lists, which then have merge sort called on these two smaller lists
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* recursively until there is only a sorted list of one.
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*
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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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* Sort and merge two given arrays
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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} merged list
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*/
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/*
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* Doctests
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* > merge([5, 4],[ 1, 2, 3])
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* [1, 2, 3, 5, 4]
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* > merge([],[1, 2])
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* [1, 2]
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* > merge([1, 2, 3], [1])
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* [1, 1, 2, 3]
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* > merge([], [])
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* []
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*
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* > mergeSort([5, 4])
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* [4, 5]
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* > mergeSort([8, 4, 10, 15, 9])
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* [4, 8, 9, 10, 15]
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* > mergeSort([1, 2, 3])
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* [1, 2, 3]
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* > mergeSort([ ])
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* [ ]
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*/
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function merge (list1, list2) {
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var results = []
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while (list1.length && list2.length) {
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if (list1[0] <= list2[0]) {
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results.push(list1.shift())
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} else {
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results.push(list2.shift())
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}
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}
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return results.concat(list1, list2)
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}
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/**
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* Break down the lists into smaller pieces to be merged
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* @param {Array} list - list to be sorted
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* @return {Array} sorted list
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*/
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function mergeSort (list) {
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if (list.length < 2) return list
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var listHalf = Math.floor(list.length / 2)
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var subList1 = list.slice(0, listHalf)
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var subList2 = list.slice(listHalf, list.length)
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return merge(mergeSort(subList1), mergeSort(subList2))
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}
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// Merge Sort Example
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var unsortedArray = [10, 5, 3, 8, 2, 6, 4, 7, 9, 1]
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var sortedArray = mergeSort(unsortedArray)
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console.log('Before:', unsortedArray, 'After:', sortedArray)
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