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| 1 | +/** |
| 2 | + * @function Timsort is a hybrid stable sorting algorithm, derived from merge sort and insertion sort, |
| 3 | + * designed to perform well on many kinds of real-world data. |
| 4 | + * It was implemented by Tim Peters in 2002 for use in the Python programming language. |
| 5 | + * It is also used to sort arrays of non-primitive type in Java SE 7, |
| 6 | + * on the Android platform, in GNU Octave, on V8, Swift and Rust. |
| 7 | + * 1) It sorts small partitions using Insertion Sort. |
| 8 | + * 2) Merges the partition using Merge Sort. |
| 9 | + * @see [Timsort](https://en.wikipedia.org/wiki/Timsort) |
| 10 | + * @param {Array} array |
| 11 | + */ |
| 12 | + |
| 13 | +const Timsort = (array) => { |
| 14 | + // Default size of a partition |
| 15 | + const RUN = 32 |
| 16 | + const n = array.length |
| 17 | + // Sorting the partitions using Insertion Sort |
| 18 | + for (let i = 0; i < n; i += RUN) { |
| 19 | + InsertionSort(array, i, Math.min(i + RUN - 1, n - 1)) |
| 20 | + } |
| 21 | + for (let size = RUN; size < n; size *= 2) { |
| 22 | + for (let left = 0; left < n; left += 2 * size) { |
| 23 | + const mid = left + size - 1 |
| 24 | + const right = Math.min(left + 2 * size - 1, n - 1) |
| 25 | + Merge(array, left, mid, right) |
| 26 | + } |
| 27 | + } |
| 28 | +} |
| 29 | + |
| 30 | +/** |
| 31 | + * @function performs insertion sort on the partition |
| 32 | + * @param {Array} array array to be sorted |
| 33 | + * @param {Number} left left index of partiton |
| 34 | + * @param {Number} right right index of partition |
| 35 | + */ |
| 36 | + |
| 37 | +const InsertionSort = (array, left, right) => { |
| 38 | + for (let i = left + 1; i <= right; i++) { |
| 39 | + const key = array[i] |
| 40 | + let j = i - 1 |
| 41 | + while (j >= left && array[j] > key) { |
| 42 | + array[j + 1] = array[j] |
| 43 | + j-- |
| 44 | + } |
| 45 | + array[j + 1] = key |
| 46 | + } |
| 47 | +} |
| 48 | + |
| 49 | +/** |
| 50 | + * @function merges two sorted partitions |
| 51 | + * @param {Array} array array to be sorted |
| 52 | + * @param {Number} left left index of partition |
| 53 | + * @param {Number} mid mid index of partition |
| 54 | + * @param {Number} right right index of partition |
| 55 | + */ |
| 56 | + |
| 57 | +const Merge = (array, left, mid, right) => { |
| 58 | + if (mid >= right) return |
| 59 | + const len1 = mid - left + 1 |
| 60 | + const len2 = right - mid |
| 61 | + const larr = Array(len1) |
| 62 | + const rarr = Array(len2) |
| 63 | + for (let i = 0; i < len1; i++) { |
| 64 | + larr[i] = array[left + i] |
| 65 | + } |
| 66 | + for (let i = 0; i < len2; i++) { |
| 67 | + rarr[i] = array[mid + 1 + i] |
| 68 | + } |
| 69 | + let i = 0; let j = 0; let k = left |
| 70 | + while (i < larr.length && j < rarr.length) { |
| 71 | + if (larr[i] < rarr[j]) { |
| 72 | + array[k++] = larr[i++] |
| 73 | + } else { |
| 74 | + array[k++] = rarr[j++] |
| 75 | + } |
| 76 | + } |
| 77 | + while (i < larr.length) { |
| 78 | + array[k++] = larr[i++] |
| 79 | + } |
| 80 | + while (j < rarr.length) { |
| 81 | + array[k++] = rarr[j++] |
| 82 | + } |
| 83 | +} |
| 84 | + |
| 85 | +/** |
| 86 | + * @example Test of Timsort functions. |
| 87 | + * Data is randomly generated. |
| 88 | + * Prints "RIGHT" if it works as expected, |
| 89 | + * otherwise "FAULTY" |
| 90 | + */ |
| 91 | +(() => { |
| 92 | + const size = 1000000 |
| 93 | + const data = Array(size) |
| 94 | + for (let i = 0; i < size; i++) { |
| 95 | + data[i] = Math.random() * Number.MAX_SAFE_INTEGER |
| 96 | + } |
| 97 | + const isSorted = function (array) { |
| 98 | + const n = array.length |
| 99 | + for (let i = 0; i < n - 1; i++) { |
| 100 | + if (array[i] > array[i + 1]) return false |
| 101 | + } |
| 102 | + return true |
| 103 | + } |
| 104 | + Timsort(data) |
| 105 | + if (isSorted(data)) { |
| 106 | + console.log('RIGHT') |
| 107 | + } else { |
| 108 | + console.log('FAULTY') |
| 109 | + } |
| 110 | +})() |
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