chore(CSharp): add character limit (#740)

Co-authored-by: Ming Tsai <37890026+ming-tsai@users.noreply.github.com>

algorithms/CSharp/README.md

@@ -22,6 +22,7 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
 ## Strings
 - [Palindrome](src/Strings/palindrome.cs)
 - [Trie](src/Strings/trie.cs)
+- [Character Limit](src/Strings/character-limit.cs)
 
 ## Search
 - [Binary Search](src/Search/binary-search.cs)

algorithms/CSharp/src/Strings/character-limit.cs

@@ -0,0 +1,50 @@
+using System;
+using System.Linq;
+
+//Time Complexity: O(N)
+namespace Algorithms.Strings
+{
+    public class TextHelper
+    {
+        public static void Main()
+        {
+            Console.WriteLine("Please enter a string");
+            string input = Console.ReadLine();
+
+            while (input == "")
+            {
+                Console.WriteLine("Please enter a string");
+                input = Console.ReadLine();
+            }
+
+            Console.WriteLine("Please enter the number of characters you want to show");
+            string input2 = Console.ReadLine();
+
+            while (!input2.All(char.IsDigit) || input2.All(char.IsWhiteSpace))
+            {
+                Console.WriteLine("The number you have entered is invalid. Please try again:");
+                input2 = Console.ReadLine();
+            }
+
+            int num = Convert.ToInt32(input2);
+            Console.WriteLine(CharacterLimit(input, num));
+        }
+
+        //Limits the the amount of characters shown in a string.
+        public static string CharacterLimit(string input, int num)
+        {
+            //converts a string to a character array
+            char[] ch = input.ToCharArray();
+
+            //loops through the array from the last element to the first, and replaces each element with a "."
+            for (int i = ch.Count(); i > num; i--)
+            {
+                ch[i - 1] = '.';
+            }
+
+            //converts character array back to string to be returned by the method
+            string output = new string(ch);
+            return output;
+        }
+    }
+}

algorithms/CSharp/test/Strings/character-limit.cs

@@ -0,0 +1,18 @@
+using NUnit.Framework;
+
+namespace Algorithms.CSharp.Test.Strings
+{
+    [TestFixture]
+    internal class Character_Limit
+    {
+        [TestCase("Hello", "Hel..")]
+        [TestCase("World", "Wor..")]
+        [TestCase("How Ya", "How...")]
+        [TestCase("Doin", "Doi.")]
+        public void PassString_ShouldGetExpectedResult(string text, string expected)
+        {
+            string result = Algorithms.Strings.TextHelper.CharacterLimit(text, 3);
+            Assert.AreEqual(expected, result);
+        }
+    }
+}