Data commit

Task/Negative-base-numbers/Kotlin/negative-base-numbers.kotlin

@@ -0,0 +1,43 @@
+// version 1.1.2
+
+const val DIGITS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+
+fun encodeNegBase(n: Long, b: Int): String {
+    require(b in -62 .. -1)
+    if (n == 0L) return "0"
+    val out = mutableListOf<Char>()
+    var nn = n
+    while (nn != 0L) {
+        var rem = (nn % b).toInt()
+        nn /= b
+        if (rem < 0) {
+            nn++
+            rem -= b
+        }
+        out.add(DIGITS[rem])
+    }
+    out.reverse()
+    return out.joinToString("")
+}
+
+fun decodeNegBase(ns: String, b: Int): Long {
+    require(b in -62 .. -1)
+    if (ns == "0") return 0
+    var total = 0L
+    var bb = 1L
+    for (c in ns.reversed()) {
+        total += DIGITS.indexOf(c) * bb
+        bb *= b
+    }
+    return total
+}
+
+fun main(args:Array<String>) {
+    val nbl = listOf(10L to -2, 146L to -3, 15L to -10, -17596769891 to -62)
+    for (p in nbl) {
+        val ns = encodeNegBase(p.first, p.second)
+        System.out.printf("%12d encoded in base %-3d = %s\n", p.first, p.second, ns)
+        val n  = decodeNegBase(ns, p.second)
+        System.out.printf("%12s decoded in base %-3d = %d\n\n", ns, p.second, n)
+    }
+}