June 2018 Update

Task/Fibonacci-word/C-sharp/fibonacci-word.cs

@@ -0,0 +1,71 @@
+using SYS = System;
+using SCG = System.Collections.Generic;
+
+//
+// Basically a port of the C++ solution as posted
+// 2017-11-12.
+//
+namespace FibonacciWord
+{
+  class Program
+  {
+    static void Main( string[] args )
+    {
+      PrintHeading();
+      string firstString = "1";
+      int n = 1;
+      PrintLine( n, firstString );
+      string secondString = "0";
+      ++n;
+      PrintLine( n, secondString );
+      while ( n < 37 )
+      {
+        string resultString = firstString + secondString;
+        firstString = secondString;
+        secondString = resultString;
+        ++n;
+        PrintLine( n, resultString );
+      }
+    }
+
+    private static void PrintLine( int n, string result )
+    {
+      SYS.Console.Write( "{0,-5}", n );
+      SYS.Console.Write( "{0,12}", result.Length );
+      SYS.Console.WriteLine( "  {0,-16}", GetEntropy( result ) );
+    }
+
+    private static double GetEntropy( string result )
+    {
+      SCG.Dictionary<char, int> frequencies = new SCG.Dictionary<char, int>();
+      foreach ( char c in result )
+      {
+        if ( frequencies.ContainsKey( c ) )
+        {
+          ++frequencies[c];
+        }
+        else
+        {
+          frequencies[c] = 1;
+        }
+      }
+
+      int length = result.Length;
+      double entropy = 0;
+      foreach ( var keyValue in frequencies )
+      {
+        double freq = (double)keyValue.Value / length;
+        entropy += freq * SYS.Math.Log( freq, 2 );
+      }
+
+      return -entropy;
+    }
+
+    private static void PrintHeading()
+    {
+      SYS.Console.Write( "{0,-5}", "N" );
+      SYS.Console.Write( "{0,12}", "Length" );
+      SYS.Console.WriteLine( "  {0,-16}", "Entropy" );
+    }
+  }
+}