Data update

Task/Bifid-cipher/Kotlin/bifid-cipher.kotlin

@@ -0,0 +1,77 @@
+import kotlin.math.sqrt
+
+data class Square(private val square: String) {
+    private val dim: Int =
+        sqrt(square.length.toDouble()).toInt()
+    fun encode(ch: Char): Pair<Int, Int> =
+        square.indexOf(ch).let { idx -> Pair(idx / dim, idx.mod(dim)) }
+    fun decode(pair: List<Int>): Char =
+        square[pair[0] * dim + pair[1]]
+    fun decode(row: Int, col: Int): Char =
+        square[row * dim + col]
+}
+
+class Bifid(private val square: Square) {
+    fun encrypt(str: String): String {
+        fun expandAndScatter(str: String): IntArray {
+            val buffer = IntArray(str.length * 2)
+            str.forEachIndexed { i, ch ->
+                with(square.encode(ch)) {
+                    buffer[i] = first
+                    buffer[str.length + i] = second
+                }
+            }
+            return buffer
+        }
+
+        val buffer = expandAndScatter(str)
+
+        val characters: List<Char> = buffer.asIterable()
+            .windowed(size = 2, step = 2)
+            .map { square.decode(it) }
+
+        return String(characters.toCharArray())
+    }
+
+    fun decrypt(str: String): String {
+        fun expand(str: String): IntArray {
+            val buffer = IntArray(str.length * 2)
+            for (i in buffer.indices step 2) {
+                with(square.encode(str[i / 2])) {
+                    buffer[i] = first
+                    buffer[1 + i] = second
+                }
+            }
+            return buffer
+        }
+
+        val buffer = expand(str)
+
+        val characters = str.toCharArray()
+        for (i in characters.indices) {
+            characters[i] = square.decode(buffer[i], buffer[characters.size + i])
+        }
+        return String(characters)
+    }
+}
+
+fun main() {
+    with (Bifid(Square("ABCDEFGHIKLMNOPQRSTUVWXYZ"))) {
+        println("\n### ABC... 5x5")
+        encrypt("ATTACKATDAWN").also { println("ATTACKATDAWN -> $it") }
+        decrypt("DQBDAXDQPDQH").also { println("DQBDAXDQPDQH -> $it") }
+    }
+    with(Bifid(Square("BGWKZQPNDSIOAXEFCLUMTHYVR"))) {
+        println("\n### BGW... 5x5")
+        encrypt("FLEEATONCE").also { println("FLEEATONCE -> $it") }
+        decrypt("UAEOLWRINS").also { println("UAEOLWRINS -> $it") }
+
+        encrypt("ATTACKATDAWN").also { println("ATTACKATDAWN -> $it") }
+        decrypt("EYFENGIWDILA").also { println("EYFENGIWDILA -> $it") }
+    }
+    with(Bifid(Square("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"))) {
+        println("\n### ABC... 6x6")
+        encrypt("THEINVASIONWILLSTARTONTHEFIRSTOFJANUARY").also { println("$it") }
+        decrypt("TBPDIPHJSPOTAIVMGPCZKNSCN09BFIHK64I7BM4").also { println("$it") }
+    }
+}