65 lines
1.6 KiB
JavaScript
65 lines
1.6 KiB
JavaScript
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/**
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* Run-length encoding.
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* The idea of this algorithm is to remove the usless zeros and
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* give us representation of string in binary which in which the
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* zeros will be stripped and replaced with their count.
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*/
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(function (exports) {
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'use strict';
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var runLengthEncoding = (function () {
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/**
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* Convers a given string to sequence of numbers
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* This takes O(n).
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*/
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function convertToAscii(str) {
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var result = [];
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var currentChar = '';
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var i = 0;
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for (; i < str.length; i += 1) {
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currentChar = str[i].charCodeAt(0).toString(2);
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currentChar = new Array(9 - currentChar.length).join('0') + currentChar;
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result.push(currentChar);
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}
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return result.join('');
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}
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/**
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* Encodes the binary string to run-length encoding.
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* Takes O(n^2).
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*/
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function runLength(vector) {
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var result = [];
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var zeros = 0;
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var zerosTemp = '';
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var i = 0;
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for (; i < vector.length; i += 1) {
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if (vector[i] === '0') {
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zeros += 1;
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} else {
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zerosTemp = zeros.toString(2);
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result.push(new Array(zerosTemp.length).join('1'));
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result.push('0' + zerosTemp);
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zeros = 0;
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}
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}
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return result.join('');
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}
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/**
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* Accepts a string and returns it's run-length
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* encoded binary representation.
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* Takes O(n^2).
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*/
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return function (str) {
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var asciiString = convertToAscii(str);
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return runLength(asciiString);
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};
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}());
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exports.runLength = runLengthEncoding;
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}(typeof exports === 'undefined' ? window : exports));
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