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91 lines
2.4 KiB
JavaScript
91 lines
2.4 KiB
JavaScript
(function (exports) {
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'use strict';
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var countingSort = (function () {
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/**
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* Gets the count of the elements into the input array.
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*
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* @private
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* @param {Array} array The input array.
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* @return {Array} The count of each element from the input array.
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*/
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function getCount(array) {
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var count = [];
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var current;
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for (var i = 0; i < array.length; i += 1) {
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current = array[i];
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count[current] = (count[current] || 0) + 1;
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}
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return count;
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}
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/**
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* Gets the count of the elements which are less than a given.
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*
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* @private
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* @param {Array} array The input array.
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* @return {Array} less The count of the elements which.
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* are less than each element from the input.
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*/
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function getLessCount(array) {
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var less = [];
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var last;
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less[0] = array[0] || 0;
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for (var i = 1; i < array.length; i += 1) {
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last = array[i - 1] || 0;
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less[i] = last + less[i - 1];
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}
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return less;
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}
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/**
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* Sorts the input array.
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*
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* @private
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* @param {Array} array Input which should be sorted.
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* @param {Array} less Count of the less elements for each element.
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* @return {Array} The sorted input.
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*/
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function sort(array, less) {
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var result = [];
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var currentPositions = [];
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var current;
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var position;
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for (var i = 0; i < array.length; i += 1) {
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current = array[i];
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position = less[current];
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if (currentPositions[current] === undefined) {
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currentPositions[current] = position;
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}
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result[currentPositions[current]] = current;
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currentPositions[current] += 1;
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}
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return result;
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}
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/**
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* Counting sort algorithm. It's correct only
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* for array of integers.<br><br>
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* Time complexity: O(N).
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*
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* @example
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* var sort = require('path-to-algorithms/src/' +
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* 'sorting/countingsort').countingSort;
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* console.log(sort([2, 5, 1, 3, 4])); // [ 1, 2, 3, 4, 5 ]
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*
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* @public
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* @module sorting/countingsort
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* @param {Array} array Array which should be sorted.
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* @return {Array} Sorted array.
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*/
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return function (array) {
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var less = getLessCount(getCount(array));
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return sort(array, less);
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};
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}());
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exports.countingSort = countingSort;
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})(typeof window === 'undefined' ? module.exports : window);
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