[COMPRESSOR] RLE

Author: ddaniel27

Compression/RLE.js

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+/*
+  * RLE (Run Length Encoding) is a simple form of data compression.
+  * The basic idea is to represent repeated successive characters as a single count and character.
+  * For example, the string "AAAABBBCCDAA" would be encoded as "4A3B2C1D2A".
+  *
+  * @author - [ddaniel27](https://github.com/ddaniel27)
+*/
+
+function Compress(str) {
+  let compressed = ''
+  let count = 1
+
+  for (let i = 0; i < str.length; i++) {
+    if (str[i] !== str[i + 1]) {
+      compressed += count + str[i]
+      count = 1
+      continue
+    }
+
+    count++
+  }
+
+  return compressed
+}
+
+function Decompress(str) {
+  let decompressed = ''
+  let match = [...str.matchAll(/(\d+)(\D)/g)] // match all groups of digits followed by a non-digit character
+
+  match.forEach(item => {
+    let [count, char] = [item[1], item[2]]
+    decompressed += char.repeat(count)
+  })
+
+	return decompressed
+}
+
+export {
+  Compress,
+  Decompress
+}

Compression/test/RLE.test.js

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+import { Compress, Decompress } from '../RLE'
+
+describe('Test RLE Compressor/Decompressor', () => {
+  it('Test - 1, Pass long repetitive strings', () => {
+    expect(Compress('AAAAAAAAAAAAAA')).toBe('14A')
+    expect(Compress('AAABBQQQQQFG')).toBe('3A2B5Q1F1G')
+  })
+
+  it('Test - 2, Pass compressed strings', () => {
+    expect(Decompress('14A')).toBe('AAAAAAAAAAAAAA')
+    expect(Decompress('3A2B5Q1F1G')).toBe('AAABBQQQQQFG')
+  })
+})