You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
65 lines
1.6 KiB
JavaScript
65 lines
1.6 KiB
JavaScript
/**
|
|
* Run-length encoding.
|
|
* The idea of this algorithm is to remove the usless zeros and
|
|
* give us representation of string in binary which in which the
|
|
* zeros will be stripped and replaced with their count.
|
|
*/
|
|
(function (exports) {
|
|
'use strict';
|
|
|
|
var runLengthEncoding = (function () {
|
|
|
|
/**
|
|
* Convers a given string to sequence of numbers
|
|
* This takes O(n).
|
|
*/
|
|
function convertToAscii(str) {
|
|
var result = [];
|
|
var currentChar = '';
|
|
var i = 0;
|
|
for (; i < str.length; i += 1) {
|
|
currentChar = str[i].charCodeAt(0).toString(2);
|
|
currentChar = new Array(9 - currentChar.length).join('0') + currentChar;
|
|
result.push(currentChar);
|
|
}
|
|
return result.join('');
|
|
}
|
|
|
|
/**
|
|
* Encodes the binary string to run-length encoding.
|
|
* Takes O(n^2).
|
|
*/
|
|
function runLength(vector) {
|
|
var result = [];
|
|
var zeros = 0;
|
|
var zerosTemp = '';
|
|
var i = 0;
|
|
for (; i < vector.length; i += 1) {
|
|
if (vector[i] === '0') {
|
|
zeros += 1;
|
|
} else {
|
|
zerosTemp = zeros.toString(2);
|
|
result.push(new Array(zerosTemp.length).join('1'));
|
|
result.push('0' + zerosTemp);
|
|
zeros = 0;
|
|
}
|
|
}
|
|
return result.join('');
|
|
}
|
|
|
|
/**
|
|
* Accepts a string and returns it's run-length
|
|
* encoded binary representation.
|
|
* Takes O(n^2).
|
|
*/
|
|
return function (str) {
|
|
var asciiString = convertToAscii(str);
|
|
return runLength(asciiString);
|
|
};
|
|
|
|
}());
|
|
|
|
exports.runLength = runLengthEncoding;
|
|
|
|
}(typeof exports === 'undefined' ? window : exports));
|