Alternating characters problem:C# solution

Added a new solution for alternating characters problem using C# programming language

Algorithms/Strings/Alternating Characters/Solution.cs

@@ -0,0 +1,47 @@
+/*
+         Problem: https://www.hackerrank.com/challenges/alternating-characters/problem
+         C# Language Version: 6.0
+         .Net Framework Version: 4.7
+         Tool Version : Visual Studio Community 2017
+         Thoughts (Key points in algorithm):
+         - We've to simply track the alternating characters while traversing the characters of the string
+         - If the character being traversed is same as previous character then we need to delete it.
+         - For delete operation don't do physical deletion of character from the string. Instead, keep a counter, increment it and move to the next character.
+         - Print the counter value in the end.
+
+         Gotchas:
+          <None>
+
+         Time Complexity:  O(n) //we need to traverse the entire string
+         Space Complexity: O(1) //we are reading every string input in a test case from console input stream character by character 
+                                  in place of saving the entire string in memory. So constant space.
+*/
+using System;
+class Solution
+{
+    static void Main(string[] args)
+    {
+        var testCaseCount = int.Parse(Console.ReadLine());
+        for (var i = 0; i < testCaseCount; i++)
+        {
+            var deletedCharactercount = 0;
+            var nextChar = Console.Read();
+            var lastChar = nextChar;
+
+            nextChar = Console.Read();
+            //special handling for hacker rank execution environment. 10 is ascii code of line feed '\n'.
+            //Hacker rank uses '\n' character for end of a test case and -1 for end of file which marks the end of last test case.
+            //while running on my own computer I compare it with ascii code of carriage return '\r' which is 13.
+            while (nextChar != 10 && nextChar != -1)
+            {
+                if (nextChar == lastChar)
+                    deletedCharactercount++;
+                else
+                    lastChar = nextChar;
+
+                nextChar = Console.Read();
+            }
+            Console.WriteLine(deletedCharactercount);
+        }
+    }
+}

README.md

@@ -169,7 +169,7 @@
 |   | [Separate the Numbers](https://www.hackerrank.com/challenges/separate-the-numbers)| <ul><li>Java</li></ul> |  | | Easy | 20| ||
 |   | [Funny String](https://www.hackerrank.com/challenges/funny-string)| <ul><li>[Java](./Algorithms/Strings/Funny%20String/Solution.java)</li><ul> | _O(n)_ | _O(1)_ | Easy | 25| ||
 |   | [Gemstones](https://www.hackerrank.com/challenges/gem-stones)| <ul><li>[Java](./Algorithms/Strings/Gemstones/Solution.java)</li><ul> | _O(n)_ | _O(n)_ | Easy | 20| ||
-|   | [Alternating Characters](https://www.hackerrank.com/challenges/alternating-characters)| <ul><li>[Java](./Algorithms/Strings/Alternating%20Characters/Solution.java)</li><ul> | _O(n)_ | _O(1)_ | Easy | 20| ||
+|   | [Alternating Characters](https://www.hackerrank.com/challenges/alternating-characters)| <ul><li>[Java](./Algorithms/Strings/Alternating%20Characters/Solution.java)</li><li>[C#](./Algorithms/Strings/Alternating%20Characters/Solution.cs)</li><ul> | _O(n)_ | _O(1)_ | Easy | 20| ||
 |   | [Beautiful Binary String](https://www.hackerrank.com/challenges/beautiful-binary-string)| <ul><li>[Java](./Algorithms/Strings/Beautiful%20Binary%20String/Solution.java)</li><ul> | _O(n)_ | _O(1)_ | Easy | 20| ||
 |   | [The Love-Letter Mystery](https://www.hackerrank.com/challenges/the-love-letter-mystery)| <ul><li>[Java](./Algorithms/Strings/The%20Love-Letter%20Mystery/Solution.java)</li><ul> | _O(n)_ | _O(1)_ | Easy | 20| ||
 |   | [Determining DNA Health](https://www.hackerrank.com/challenges/determining-dna-health)| <ul><li>Java</li></ul> |  | | Hard | 50| ||