Data commit

Task/LZW-compression/Groovy/lzw-compression-1.groovy

@@ -0,0 +1,37 @@
+def compress = { text ->
+    def dictionary = (0..<256).inject([:]) { map, ch -> map."${(char)ch}" = ch; map }
+    def w = '', compressed = []
+    text.each { ch ->
+        def wc = "$w$ch"
+        if (dictionary[wc]) {
+            w = wc
+        } else {
+            compressed << dictionary[w]
+            dictionary[wc] = dictionary.size()
+            w = "$ch"
+        }
+    }
+    if (w) { compressed << dictionary[w] }
+    compressed
+}
+
+def decompress = { compressed ->
+    def dictionary = (0..<256).inject([:])  { map, ch -> map[ch] = "${(char)ch}"; map }
+    int dictSize = 128;
+    String w = "${(char)compressed[0]}"
+    StringBuffer result = new StringBuffer(w)
+
+    compressed.drop(1).each { k ->
+        String entry = dictionary[k]
+        if (!entry) {
+            if (k != dictionary.size()) throw new IllegalArgumentException("Bad compressed k $k")
+            entry = "$w${w[0]}"
+        }
+        result << entry
+
+        dictionary[dictionary.size()] = "$w${entry[0]}"
+        w = entry
+    }
+
+    result.toString()
+}

Task/LZW-compression/Groovy/lzw-compression-2.groovy

@@ -0,0 +1,8 @@
+def plaintext = 'TOBEORNOTTOBEORTOBEORNOT'
+def compressed = compress(plaintext)
+def result = decompress(compressed)
+
+println """\
+    Plaintext:    '$plaintext'
+    Compressed:   $compressed
+    Uncompressed: '$result'""".stripIndent()