101 lines
2.8 KiB
JavaScript
101 lines
2.8 KiB
JavaScript
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(function (exports) {
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'use strict';
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var radixSort = (function () {
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/**
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* Returns the digit of a number that is 'lsdOffset'
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* places from the least significant digit.
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*
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* @private
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* @param {Number} number Number
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* @param {Number} lsdOffset Offset of the digit to return, counting
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* from the position of the least significant digit (e.g. lsdOffset = 0
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* will return the least significant digit itself)
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* @return {String} digit The specified number digit. Returns 'undefined'
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* if lsdOffset is bigger or equal to the number of digits of the 'number'
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* argument.
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*/
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var getDigit = function (number, lsdOffset) {
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var size = number.toString().length;
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var digit;
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if (lsdOffset >= 0 && lsdOffset < size) {
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digit = number.toString()[size - 1 - lsdOffset];
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}
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return digit;
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};
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/**
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* Least significant digit (LSD) Radix sort. A non-comparative,
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* stable integer sorting algorithm.<br><br>
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* Worst-case time complexity is O(N K) for N keys with K being
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* the average key length, measured in number of digits.
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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/radixsort').radixSort;
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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/radixsort
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* @param {Array} array Input integer array
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* @return {Array} Sorted array
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*/
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return function (array) {
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var size = array.length;
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var R = 10; /* Alphabet size ([0-9] for integers) */
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var count;
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var digit;
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var i;
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var j;
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/* Find maximum key size */
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var maxKeySize = (array[0] || '').toString().length;
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for (i = 1; i < size; i += 1) {
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var numStr = array[i].toString();
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if (numStr.length > maxKeySize) {
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maxKeySize = numStr.length;
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}
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}
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for (i = 0; i < maxKeySize; i += 1) {
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/* Initialize count */
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count = [];
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for (j = 0; j < R; j += 1) {
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count[j] = 0;
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}
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/* Count frequency of each array element */
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for (j = 0; j < size; j += 1) {
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digit = getDigit(array[j], i) || 0;
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count[digit] += 1;
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}
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/* Compute cumulates */
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for (j = 1; j < R; j += 1) {
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count[j] += count[j - 1];
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}
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/* Move elements to auxiliary array */
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var aux = [];
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for (j = size - 1; j >= 0; j -= 1) {
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digit = getDigit(array[j], i) || 0;
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count[digit] -= 1;
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aux[count[digit]] = array[j];
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}
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/* Copy elements back from auxilary array */
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for (j = 0; j < size; j += 1) {
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array[j] = aux[j];
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}
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}
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return array;
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};
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})();
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exports.radixSort = radixSort;
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})(typeof window === 'undefined' ? module.exports : window);
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