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