[Compressor] RLE Compressor implementation (TheAlgorithms#1671)

ddaniel27 · appgurueu · web-flow · commit 5f8d4d447a85 · 2024-06-23T10:50:25.000+05:30
* [Solution] Project euler challenge 19 with tests

* update leap year function

* Remove unnecessary, confusingly placed comments

* [COMPRESSOR] RLE

* [COMPRESSOR] RLE style fixed

---------

Co-authored-by: Lars Müller &lt;34514239+appgurueu@users.noreply.github.com&gt;
diff --git a/Compression/RLE.js b/Compression/RLE.js
@@ -0,0 +1,38 @@
+/*
+ * 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 }
diff --git a/Compression/test/RLE.test.js b/Compression/test/RLE.test.js
@@ -0,0 +1,13 @@
+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')
+  })
+})
