Data commit

Task/Negative-base-numbers/C-sharp/negative-base-numbers.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NegativeBaseNumbers {
+    class Program {
+        const string DIGITS = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+        static string EncodeNegativeBase(long n, int b) {
+            if (b < -62 || b > -1) {
+                throw new ArgumentOutOfRangeException("b");
+            }
+            if (n == 0) {
+                return "0";
+            }
+            StringBuilder output = new StringBuilder();
+            long nn = n;
+            while (nn != 0) {
+                int rem = (int)(nn % b);
+                nn /= b;
+                if (rem < 0) {
+                    nn++;
+                    rem -= b;
+                }
+                output.Append(DIGITS[rem]);
+            }
+            return new string(output.ToString().Reverse().ToArray());
+        }
+
+        static long DecodeNegativeBase(string ns, int b) {
+            if (b < -62 || b > -1) {
+                throw new ArgumentOutOfRangeException("b");
+            }
+            if (ns == "0") {
+                return 0;
+            }
+            long total = 0;
+            long bb = 1;
+            for (int i = ns.Length - 1; i >= 0; i--) {
+                char c = ns[i];
+                total += DIGITS.IndexOf(c) * bb;
+                bb *= b;
+            }
+            return total;
+        }
+
+        static void Main(string[] args) {
+            List<Tuple<long, int>> nbl = new List<Tuple<long, int>>() {
+                new Tuple<long, int>(10,-2),
+                new Tuple<long, int>(146,-3),
+                new Tuple<long, int>(15,-10),
+                new Tuple<long, int>(-34025238427,-62),
+            };
+            foreach (var p in nbl) {
+                string ns = EncodeNegativeBase(p.Item1, p.Item2);
+                Console.WriteLine("{0,12} encoded in base {1,-3} = {2}", p.Item1, p.Item2, ns);
+                long n = DecodeNegativeBase(ns, p.Item2);
+                Console.WriteLine("{0,12} decoded in base {1,-3} = {2}", ns, p.Item2, n);
+                Console.WriteLine();
+            }
+        }
+    }
+}