using System; using System.Linq; using System.Text.RegularExpressions; // https://www.sololearn.com/Discuss/811804/?ref=app namespace SoloLearn { class Program { static void Main(string[] zephyr_koo) { foreach (var repeatingDecimal in new string[] { ".(2)", // 2/9 ".(3)", // 1/3 ".(9)", // 1/1 ".1(23)", // 61/495 ".(142857)", // 1/7 ".9(87)" // 163/165 }) { var matcher = Regex.Match(repeatingDecimal, @".(\d*)$(\d+)$"); var repeatingPart = matcher.Groups[2].ToString(); var nonRepeatingPart = matcher.Groups[1].ToString(); var repeatingFraction = GetFraction(repeatingPart); var nonRepeatingFraction = string.IsNullOrEmpty(nonRepeatingPart) ? new Tuple(0, 1) : new Tuple( Int32.Parse(nonRepeatingPart), (int)Math.Pow(10, nonRepeatingPart.Length)); var adjustedRepeatingFraction = new Tuple( repeatingFraction.Item1, repeatingFraction.Item2 * (int)Math.Pow(10, nonRepeatingPart.Length)); var fractionRepresentation = AddFraction(adjustedRepeatingFraction, nonRepeatingFraction); Console.WriteLine($"{ repeatingDecimal.ToEllipsis() } = { fractionRepresentation.ToFraction() }"); Console.WriteLine(); } } static Tuple AddFraction(Tuple fraction1, Tuple fraction2) { var numerator = fraction1.Item1 * fraction2.Item2 + fraction2.Item1 * fraction1.Item2; var demominator = fraction1.Item2 * fraction2.Item2; var hcf = GetHCF(numerator, demominator); return new Tuple(numerator / hcf, demominator / hcf); } static Tuple GetFraction(string strPeriodicMantissa) { int mantissa = Int32.Parse(strPeriodicMantissa); var denominator = Int32.Parse(new string(Enumerable.Repeat('9', strPeriodicMantissa.Length).ToArray())); var hcf = GetHCF(mantissa, denominator); return new Tuple(mantissa / hcf, denominator / hcf); } static int GetHCF(int num1, int num2) { for (int factor = Math.Min(num1, num2); factor > 1; factor--) { if (num1 % factor == 0 && num2 % factor == 0) { return factor; } } return 1; } } static class StringFormatter { public static string ToFraction(this Tuple fraction) { return string.Concat(fraction.Item1, "/", fraction.Item2); } public static string ToEllipsis(this string repeatingDecimal) { var matcher = Regex.Match(repeatingDecimal, @".(\d*)$(\d+)$"); var repeatingPart = matcher.Groups[2].ToString(); var nonRepeatingPart = matcher.Groups[1].ToString(); return string.Concat("0.", nonRepeatingPart, new string(Enumerable.Repeat(repeatingPart, 3) .SelectMany(c => c).ToArray()), "..."); } } }

Repeating Decimal Challenge