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104 lines
2.8 KiB
JavaScript
104 lines
2.8 KiB
JavaScript
(function (exports) {
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/**
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* Mergesort module.
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*/
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'use strict';
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var ll = require('../data-structures/linked-list.js');
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function compare(a, b) {
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return a - b;
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}
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/**
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* Mergesort method which is recursively called for sorting the input array.
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*
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* @public
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* @module sorting/mergesort
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* @param {Array} array The array which should be sorted.
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* @param {Function} cmp Compares two items in an array.
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* @param {Number} start Left side of the subarray.
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* @param {Number} end Right side of the subarray.
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* @returns {Array} Array with sorted subarray.
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*
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* @example
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* var array = [2, 4, 1, 5, 6, 7];
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* var mergeSort =
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* require('path-to-algorithms/src/sorting/mergesort').mergeSort;
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* mergeSort(array); // [1, 2, 4, 5, 6, 7]
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*/
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function mergeSort(array, cmp, start, end) {
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cmp = cmp || compare;
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start = start || 0;
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end = end || array.length;
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if (Math.abs(end - start) <= 1) {
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return [];
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}
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var middle = Math.ceil((start + end) / 2);
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mergeSort(array, cmp, start, middle);
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mergeSort(array, cmp, middle, end);
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return mergeSort.merge(array, cmp, start, middle, end);
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}
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/**
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* Devides and sort merges two subarrays of given array
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*
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* @public
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* @module sorting/mergesort/merge
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* @param {Array} array The array which subarrays should be sorted.
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* @param {Number} start The start of the first subarray.
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* This subarray is with end middle - 1.
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* @param {Number} middle The start of the second array.
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* @param {Number} end end - 1 is the end of the second array.
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* @returns {Array} The array with sorted subarray.
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*
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* @example
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* var array = [1, 2, 3, 1, 4, 5, 6];
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* var merge =
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* require('path-to-algorithms/src/sorting/mergesort').merge;
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* merge(array, function (a, b) { // [1, 1, 2, 3, 4, 5, 6]
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* return a - b;
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* }, 0, 4, 7);
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*/
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mergeSort.merge = function (array, cmp, start, middle, end) {
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var left = new ll.LinkedList();
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var right = new ll.LinkedList();
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var leftSize = middle - start;
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var rightSize = end - middle;
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var maxSize = Math.max(leftSize, rightSize);
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var size = end - start;
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var i;
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for (i = 0; i < maxSize; i += 1) {
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if (i < leftSize) {
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left.push(array[start + i]);
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}
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if (i < rightSize) {
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right.push(array[middle + i]);
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}
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}
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i = 0;
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while (i < size) {
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if (left.first && right.first) {
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if (cmp(left.first.data, right.first.data) > 0) {
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array[start + i] = right.shift().data;
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} else {
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array[start + i] = left.shift().data;
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}
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} else if (left.first) {
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array[start + i] = left.shift().data;
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} else {
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array[start + i] = right.shift().data;
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}
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i += 1;
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}
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return array;
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};
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exports.mergeSort = mergeSort;
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}(typeof exports === 'undefined' ? window : exports));
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