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GeezerVison is showing github.com — JavaScript/Sorts/IntroSort.js at master · TheAlgorithms/JavaScript Expand file tree/ Copy pathIntroSort.jsMore file actions 309 lines (306 loc) · 8.45 KB / Copy pathIntroSort.jsFile metadata and controls309 lines (306 loc) · 8.45 KB 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 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* @author [Lakhan Nad](https://github.com/Lakhan-Nad) */ function introsort(array, compare) { /** * @function Default Comparison Function * This function is same as implemented by * Array.sort method * @see [StackOverflow](https://stackoverflow.com/questions/47334234/how-to-implement-array-prototype-sort-default-compare-function) * @param {*} a variable 1 * @param {*} b variable 2 * @returns {Number} * -1 if a is less than b * 0 if a is equal to b * 1 if a greater than b */ const defaultComparator = function (x, y) { if (x === undefined && y === undefined) return 0 if (x === undefined) return 1 if (y === undefined) return -1 const xString = toString(x) const yString = toString(y) if (xString < yString) return -1 if (xString > yString) return 1 return 0 } /** * @function helper function for defaultComparator * Converts a given object to String * @throws TypeError() * @param {Object} obj * @returns {String} String representation of given object */ const toString = function (obj) { if (obj === null) return 'null' if (typeof obj === 'boolean' || typeof obj === 'number') { return obj.toString() } if (typeof obj === 'string') return obj if (typeof obj === 'symbol') throw new TypeError() return obj.toString() } /** * Checks if the value passed is an array * or not */ if (Array.isArray(array) === false) { return } /** * If the compare parameter is not a function * or not passed at all use default comparator * function */ if (typeof compare !== 'function') { compare = defaultComparator // If compare is not a comparator function } /** * Use a closure to define the whole sort * implementation this is done through * [IIFE](https://en.wikipedia.org/wiki/Immediately_invoked_function_expression) */ return (function (array, comparator) { const swap = function (index1, index2) { const temp = array[index1] array[index1] = array[index2] array[index2] = temp } /** * @constant THRESHOLD * If the length of array is less than * this then we simply perform insertion sort */ const THRESHOLD = 16 /** * @constant TUNEMAXDEPTH * Constant used to increase or decrease value * of maxDepth */ const TUNEMAXDEPTH = 1 const len = array.length /** * Return if array is only of length 1 * Array of size 1 is always sorted */ if (len === 1) { return } /** * Calculate maxDepth = log2(len) * Taken from implementation in stdc++ */ const maxDepth = Math.floor(Math.log2(len)) * TUNEMAXDEPTH /** * The very first call to quicksort * this initiates sort routine */ quickSort(0, len, maxDepth) /** * A final check call to insertion sort * on sorted array */ insertionSort(0, len) /** ********************* Implementation of various routines **************************/ /** * @function * This is recursive quicksort implementation in array * of segment [start,last-1] * [QuickSort](https://en.wikipedia.org/wiki/Quicksort) * @param {Number} start the start index of array segment to be sorted * @param {Number} last one more than the last index of array segment * @param {Number} depth this measures how many recursive calls are done */ function quickSort(start, last, depth) { if (last - start <= THRESHOLD) { insertionSort(start, last) return } else if (depth <= 0) { heapSort(start, last) return } let pivot = (last + start) >> 1 pivot = partition(start, last, pivot) quickSort(start, pivot, depth - 1) quickSort(pivot + 1, last, depth - 1) } /** * @function Helper function to quicksort * @param {Number} start the start of array segment to partition * @param {Number} last one more than last index of the array segment * @param {Number} pivot the index of pivot to be used * @returns {Number} the index of pivot after partition */ function partition(start, last, pivot) { swap(start, pivot) pivot = start let lo = start let hi = last while (true) { lo++ while (comparator(array[lo], array[pivot]) <= 0 && lo !== last) { lo++ } hi-- while (comparator(array[hi], array[pivot]) > 0 && hi !== start) { hi-- } if (lo >= hi) { break } swap(lo, hi) } swap(start, hi) return hi } /** * @function * Performs insertion sort on array of range * [start, last-1] * @param {Number} start the first index of array segment to be sorted * @param {Number} last one more than last index of array to be sorted */ function insertionSort(start, last) { let i, j for (i = start + 1; i < last; i++) { j = i - 1 while (j >= 0 && comparator(array[j], array[j + 1]) > 0) { swap(j, j + 1) j-- } } } /** * @function * Performs heapsort in array segment of range [start, last-1] * [HeapSort](https://en.wikipedia.org/wiki/Heapsort) * @param {Number} start the first index of array segment to be sorted * @param {Number} last one more than last index of array to be sorted */ function heapSort(start, last) { let x = (last + start) >> 1 while (x - start >= 0) { heapify(x, start, last) x-- } x = last - 1 while (x - start > 0) { swap(start, x) heapify(start, start, x) x-- } } /** * @function Helper function to heapsort routine * @param {Number} cur the index we need to heapify * @param {Number} start the start index of array segment that cur belongs to * @param {Number} last one more than last index of segment that cur belongs to */ function heapify(cur, start, last) { const size = last - start let max, lt, rt cur = cur - start while (true) { max = cur lt = 2 * max + 1 rt = 2 * max + 2 if ( lt < size && comparator(array[start + max], array[start + lt]) < 0 ) { max = lt } if ( rt < size && comparator(array[start + max], array[start + rt]) < 0 ) { max = rt } if (max !== cur) { swap(start + cur, start + max) cur = max } else { break } } } })(array, compare) } /** * @example Demo run of the sort routine * The data is randomly generated * Returns 'RIGHT:)' if the sort routine worked as expected, * 'WRONG!!' otherwise */ function demo1() { const data = [] const size = 1000000 let i = 0 let temp const c = function (a, b) { return a - b } for (i = 0; i < size; i++) { temp = Math.random() * Number.MAX_SAFE_INTEGER data.push(temp) } introsort(data, c) let faulty = false for (i = 1; i < size; i++) { if (data[i] < data[i - 1]) { faulty = true break } } if (faulty) { return 'WRONG!!' } else { return 'RIGHT:)' } } /** * @example Demo run of the sort routine * using the default compare function and * comparing the results with Array.sort */ function demo2() { const data = [] const data2 = [] const size = 1000000 let i = 0 let temp for (i = 0; i < size; i++) { temp = Math.random() * Number.MAX_SAFE_INTEGER data.push(temp) data2.push(temp) } introsort(data) data2.sort() let faulty = false for (i = 1; i < size; i++) { if (data[i] !== data2[i]) { faulty = true break } } if (faulty) { return 'WRONG Implemented Comparator!!' } else { return 'Comparator Works Fine:)' } } export { introsort, demo1, demo2 } |
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