Initial data commit

Task/Convert-decimal-number-to-rational/C-sharp/convert-decimal-number-to-rational.cs

@@ -0,0 +1,75 @@
+using System;
+using System.Text;
+
+namespace RosettaDecimalToFraction
+{
+    public class Fraction
+    {
+        public Int64 Numerator;
+        public Int64 Denominator;
+        public Fraction(double f, Int64 MaximumDenominator = 4096)
+        {
+            /* Translated from the C version. */
+            /*  a: continued fraction coefficients. */
+            Int64 a;
+            var h = new Int64[3] { 0, 1, 0 };
+            var k = new Int64[3] { 1, 0, 0 };
+            Int64 x, d, n = 1;
+            int i, neg = 0;
+
+            if (MaximumDenominator <= 1)
+            {
+                Denominator = 1;
+                Numerator = (Int64)f;
+                return;
+            }
+
+            if (f < 0) { neg = 1; f = -f; }
+
+            while (f != Math.Floor(f)) { n <<= 1; f *= 2; }
+            d = (Int64)f;
+
+            /* continued fraction and check denominator each step */
+            for (i = 0; i < 64; i++)
+            {
+                a = (n != 0) ? d / n : 0;
+                if ((i != 0) && (a == 0)) break;
+
+                x = d; d = n; n = x % n;
+
+                x = a;
+                if (k[1] * a + k[0] >= MaximumDenominator)
+                {
+                    x = (MaximumDenominator - k[0]) / k[1];
+                    if (x * 2 >= a || k[1] >= MaximumDenominator)
+                        i = 65;
+                    else
+                        break;
+                }
+
+                h[2] = x * h[1] + h[0]; h[0] = h[1]; h[1] = h[2];
+                k[2] = x * k[1] + k[0]; k[0] = k[1]; k[1] = k[2];
+            }
+            Denominator = k[1];
+            Numerator = neg != 0 ? -h[1] : h[1];
+        }
+        public override string ToString()
+        {
+            return string.Format("{0} / {1}", Numerator, Denominator);
+        }
+    }
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.OutputEncoding = UTF8Encoding.UTF8;
+            foreach (double d in new double[] { 0.9054054, 0.518518, 0.75, 0.4285714, 0.833333,
+                0.90909, 3.14159265358979, 2.7182818284590451 })
+            {
+                var f = new Fraction(d, d >= 2 ? 65536 : 4096);
+                Console.WriteLine("{0,20} → {1}", d, f);
+
+            }
+        }
+    }
+}