roman numerals

src/Scratch/RomanNumerals/RomanTests.cs

@@ -0,0 +1,191 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using FluentAssert;
+using NUnit.Framework;
+
+namespace Scratch.RomanNumerals
+{
+	/// <summary>
+	/// inspired by: http://www.sandimetz.com/blog/2016/6/9/make-everything-the-same
+	/// </summary>
+	public static class Roman
+	{
+		private static readonly IDictionary<int, string> Numerals = new Dictionary<int, string>
+		{
+			{1, "I"},
+			{4, "IV"},
+			{5, "V"},
+			{9, "IX"},
+			{10, "X"},
+			{40, "XL"},
+			{50, "L"},
+			{90, "XC"},
+			{100, "C"},
+			{400, "CD"},
+			{500, "D"},
+			{900, "CM"},
+			{1000, "M"}
+		};
+
+		public static int FromRoman(this string roman)
+		{
+			var value = 0;
+			foreach (var kvp in Numerals.OrderByDescending(x => x.Key))
+			{
+				while (roman.StartsWith(kvp.Value))
+				{
+					value += kvp.Key;
+					roman = roman.Substring(kvp.Value.Length);
+				}
+			}
+			return value;
+		}
+
+		public static string ToRoman(this int i)
+		{
+			var result = "";
+			while (i > 0)
+			{
+				foreach (var kvp in Numerals.OrderByDescending(x => x.Key))
+				{
+					while (i >= kvp.Key)
+					{
+						result += kvp.Value;
+						i -= kvp.Key;
+					}
+				}
+			}
+			return result;
+		}
+	}
+
+	public class RomanTests
+	{
+		[TestFixture]
+		public class When_asked_to_convert_and_integer_value_to_roman_numerals
+		{
+			[Test]
+			public void Given_1_should_get_I()
+			{
+				1.ToRoman().ShouldBeEqualTo("I");
+			}
+
+
+			[Test]
+			public void Given_2_should_get_II()
+			{
+				2.ToRoman().ShouldBeEqualTo("II");
+			}
+
+			[Test]
+			public void Given_4_should_get_IV()
+			{
+				4.ToRoman().ShouldBeEqualTo("IV");
+			}
+
+			[Test]
+			public void Given_5_should_get_V()
+			{
+				5.ToRoman().ShouldBeEqualTo("V");
+			}
+
+			[Test]
+			public void Given_9_should_get_IX()
+			{
+				9.ToRoman().ShouldBeEqualTo("IX");
+			}
+
+			[Test]
+			public void Given_10_should_get_X()
+			{
+				10.ToRoman().ShouldBeEqualTo("X");
+			}
+
+			[Test]
+			public void Given_40_should_get_XL()
+			{
+				40.ToRoman().ShouldBeEqualTo("XL");
+			}
+
+			[Test]
+			public void Given_50_should_get_L()
+			{
+				50.ToRoman().ShouldBeEqualTo("L");
+			}
+
+			[Test]
+			public void Given_90_should_get_XC()
+			{
+				90.ToRoman().ShouldBeEqualTo("XC");
+			}
+
+			[Test]
+			public void Given_100_should_get_C()
+			{
+				100.ToRoman().ShouldBeEqualTo("C");
+			}
+
+			[Test]
+			public void Given_400_should_get_CD()
+			{
+				400.ToRoman().ShouldBeEqualTo("CD");
+			}
+
+			[Test]
+			public void Given_500_should_get_D()
+			{
+				500.ToRoman().ShouldBeEqualTo("D");
+			}
+
+			[Test]
+			public void Given_900_should_get_CM()
+			{
+				900.ToRoman().ShouldBeEqualTo("CM");
+			}
+
+			[Test]
+			public void Given_1000_should_get_M()
+			{
+				1000.ToRoman().ShouldBeEqualTo("M");
+			}
+		}
+
+		[TestFixture]
+		public class When_asked_to_convert_roman_numerals_to_an_integer
+		{
+			[Test]
+			public void Given_I_should_get_1()
+			{
+				"I".FromRoman().ShouldBeEqualTo(1);
+			}
+
+			[Test]
+			public void Given_II_should_get_2()
+			{
+				"II".FromRoman().ShouldBeEqualTo(2);
+			}
+
+			[Test]
+			public void Given_IV_should_get_4()
+			{
+				"IV".FromRoman().ShouldBeEqualTo(4);
+			}
+		}
+
+		[TestFixture]
+		public class When_asked_to_round_trip_integer_to_roman_numerals_to_integer
+		{
+			[Test]
+			public void Should_be_able_to_convert_all_integers_between_1_and_10000()
+			{
+				for (int input = 1; input <= 10000; input++)
+				{
+					var result = input.ToRoman();
+					var roundTripped = result.FromRoman();
+					input.ShouldBeEqualTo(roundTripped);
+				}
+			}
+		}
+	}
+}

src/Scratch/Scratch.csproj

@@ -102,6 +102,9 @@
     <Compile Include="Parse\CommaSeparatedList.cs" />
     <Compile Include="Parse\TabDelimitedSerialized.cs" />
     <Compile Include="Rectangle\Demo.cs" />
+    <Compile Include="RomanNumerals\RomanTests.cs">
+      <SubType>Code</SubType>
+    </Compile>
     <Compile Include="SequentialLinq\SplitByBreakInSequence.cs" />
     <Compile Include="SequentialLinq\Tests.cs" />
     <Compile Include="Sorting\QuickSortWithInsertionSort\Class1.cs" />