Cahnges overview:

Add StringCompression.

CodingInterview.Tests/CodingInterview.Tests.csproj

@@ -37,6 +37,7 @@
     <Compile Include="Sort\MergeSortTests.cs" />
     <Compile Include="Sort\QuickSortTests.cs" />
     <Compile Include="Sort\HeapSortTests.cs" />
+    <Compile Include="CrackingTheCodingInterview\DataStructures\StringCompressionTests.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="packages.config" />
@@ -49,6 +50,8 @@
   </ItemGroup>
   <ItemGroup>
     <Folder Include="Sort\" />
+    <Folder Include="CrackingTheCodingInterview\" />
+    <Folder Include="CrackingTheCodingInterview\DataStructures\" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file

CodingInterview.Tests/CrackingTheCodingInterview/DataStructures/StringCompressionTests.cs

+// 
+//
+// This file - StringCompressionTests.cs was created by Dmytro Bogatov (dmytro@dbogatov.org)
+// on 12/7/2016, 3:47 PM
+
+using NUnit.Framework;
+
+namespace CrackingTheCodingInterview.DataStructures
+{
+	[TestFixture]
+	public class StringCompressionTests
+	{
+		[Test]
+		public void TestCases()
+		{
+			StringAssert.AreEqualIgnoringCase("a2b1c5a3", StringCompression.Compress("aabcccccaaa"));
+			StringAssert.AreEqualIgnoringCase("abcd", StringCompression.Compress("abcd"));
+			StringAssert.AreEqualIgnoringCase("", StringCompression.Compress(""));
+			StringAssert.AreEqualIgnoringCase("a", StringCompression.Compress("a"));
+			StringAssert.AreEqualIgnoringCase("aaabcdefgh", StringCompression.Compress("aaabcdefgh"));
+		}
+	}
+}

CodingInterview/CodingInterview.csproj

@@ -37,9 +37,12 @@
     <Compile Include="Sort\MergeSort.cs" />
     <Compile Include="Sort\QuickSort.cs" />
     <Compile Include="Sort\HeapSort.cs" />
+    <Compile Include="CrackingTheCodingInterview\DataStructures\StringCompression.cs" />
   </ItemGroup>
   <ItemGroup>
     <Folder Include="Sort\" />
+    <Folder Include="CrackingTheCodingInterview\" />
+    <Folder Include="CrackingTheCodingInterview\DataStructures\" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file

CodingInterview/CrackingTheCodingInterview/DataStructures/StringCompression.cs

+// 
+//
+// This file - StringCompression.cs was created by Dmytro Bogatov (dmytro@dbogatov.org)
+// on 12/7/2016, 3:44 PM
+
+/*
+ * Implement a method to perform basic string compression using the counts of repeated characters. 
+ * For example, the string aabcccccaaa would become a2blc5a3. 
+ * If the "compressed" string would not become smaller than the original string, 
+ * your method should return the original string.
+ */
+
+namespace CrackingTheCodingInterview.DataStructures
+{
+	public class StringCompression
+	{
+		public static string Compress(string input)
+		{
+			if (input.Length < 2)
+			{
+				return input;
+			}
+
+			string output = "";
+
+			var current = input[0];
+			var count = 1;
+
+			for (int i = 1; i < input.Length; i++)
+			{
+				var newChar = input[i];
+
+				if (newChar != current)
+				{
+					output += current + count.ToString();
+					current = newChar;
+					count = 1;
+				}
+				else
+				{
+					count++;
+				}
+			}
+
+			output += current + count.ToString();
+
+			return output.Length < input.Length ? output : input;
+		}
+	}
+}