add Kotlin solution for problem neetcode-gh#271

Author: technophilist

kotlin/0271-encode-and-decode-strings.kt

@@ -0,0 +1,43 @@
+package kotlin
+
+class Codec {
+    // Encodes a list of strings to a single string.
+    fun encode(strs: List<String>): String {
+        val stringBuilder = StringBuilder()
+        for (string in strs) {
+            for (char in string) {
+                stringBuilder.append(char.toInt()) // char.code in newer version's of Kotlin
+                stringBuilder.append(CHAR_DELIMITER)
+            }
+            stringBuilder.append(STRING_DELIMITER)
+        }
+        return stringBuilder.toString()
+    }
+
+    // Decodes a single string to a list of strings.
+    fun decode(s: String): List<String> {
+        val stringBuilder = StringBuilder()
+        val resultantList = mutableListOf<String>()
+        var i = 0
+        while (i in s.indices) {
+            while (s[i] != STRING_DELIMITER) {
+                var charIntegerValue = ""
+                while (s[i] != CHAR_DELIMITER) {
+                    charIntegerValue += s[i]
+                    i++
+                }
+                stringBuilder.append(charIntegerValue.toInt().toChar())
+                i++
+            }
+            resultantList.add(stringBuilder.toString())
+            stringBuilder.clear()
+            i++
+        }
+        return resultantList
+    }
+
+    companion object {
+        private const val CHAR_DELIMITER = '|'
+        private const val STRING_DELIMITER = '/'
+    }
+}