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86d333ee94
* chore: Switch to Node 20 + Vitest * chore: migrate to vitest mock functions * chore: code style (switch to prettier) * test: re-enable long-running test Seems the switch to Node 20 and Vitest has vastly improved the code's and / or the test's runtime! see #1193 * chore: code style * chore: fix failing tests * Updated Documentation in README.md * Update contribution guidelines to state usage of Prettier * fix: set prettier printWidth back to 80 * chore: apply updated code style automatically * fix: set prettier line endings to lf again * chore: apply updated code style automatically --------- Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
82 lines
2.5 KiB
JavaScript
82 lines
2.5 KiB
JavaScript
/*
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* Unlike a traditional sorting algorithm, which attempts to sort with the fewest
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* comparisons possible, the goal of pancake sort is to sort the sequence in as few reversals as
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* possible. The idea is to do something similar to Selection Sort. We one by one place
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* maximum element at the end and reduce the size of current array by one.
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*
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* Source: https://www.geeksforgeeks.org/pancake-sorting/
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*
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* This sorting algorithm is inspired by the pancake problem (hence the name),
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* where a spatula can be placed anywhere between two pancakes and flip all pancakes
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* above.
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*
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* The interesting about this algorithm (besides its name) is that instead of comparisons,
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* the algorithm relies on flipping an array.
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*
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* Source: https://en.wikipedia.org/wiki/Pancake_sorting#The_original_pancake_problem
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*
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*/
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/**
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* Unlike Array.prototype.reverse, flipArray reverses only a subarray of the given
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* array, determined by the parameters startIndex and endIndex
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*
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* @param {number[]} array The array to flip
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* @param {number} startIndex The start of the subarray
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* @param {number} endIndex The end of the subarray
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* @returns The flipped array
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*/
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export function flipArray(array, startIndex, endIndex) {
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while (startIndex < endIndex) {
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// swap front and back of the subarray
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const temp = array[startIndex]
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array[startIndex] = array[endIndex]
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array[endIndex] = temp
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// essentially reducing the problem to a smaller subarray
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startIndex++
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endIndex--
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}
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return array
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}
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/**
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* Returns the index of the maximum number of a subarray in a given array
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*
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* @param {number[]} array The array to found the maximum number's index
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* @param {*} startIndex The start of the subarray
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* @param {*} endIndex The end of the subarray
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* @returns The index of the maximum number
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*/
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export function findMax(array, startIndex, endIndex) {
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let maxIndex = 0
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for (let i = startIndex; i <= endIndex; i++) {
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if (array[i] > array[maxIndex]) maxIndex = i
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}
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return maxIndex
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}
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/**
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* The Pancake Sort algorithm.
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*
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* Note that even though it's a completely different concept of sorting an
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* array, it's rather simple!
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*
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* @param {number[]} array The array to sort
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* @returns The sorted array
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*/
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export function pancakeSort(array) {
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for (let subarraySize = array.length; subarraySize > 1; subarraySize--) {
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const maximumIndex = findMax(array, 0, subarraySize - 1)
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if (maximumIndex !== subarraySize - 1) {
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flipArray(array, 0, maximumIndex)
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flipArray(array, 0, subarraySize - 1)
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}
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}
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return array
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}
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