chore(csharp): Abundant Number (#357)

algorithms/CSharp/README.md

@@ -12,3 +12,6 @@ For running the `.cs` file please using [.Net Finddle](https://dotnetfiddle.net/
 
 ## Search
 - [Binary Search](src/Search/binary-search.cs)
+
+## Maths
+- [Abundant Number](src/Maths/abundant-number.cs)

algorithms/CSharp/src/Maths/abundant-number.cs

@@ -0,0 +1,55 @@
+/* Program to check whether a number is abundant or not */
+using System;
+
+namespace Abundant.Number
+{
+    class Abundant
+    {
+        // function to check whether number is abundant or not
+        public static bool IsAbudant(int num)
+          {
+            int i, sum = 0;
+            // loop run until it is less than or equal to half of the number
+            for (i = 1; i <= num / 2; i++)
+             {
+                // if the remainder becomes 0 add that number to sum
+                if (num % i == 0)
+                    sum += i;
+             }
+            // if the sum is greater than num that means it is an abundant number
+            if (sum > num)
+             {
+                return true;
+             }
+            else // it is not an abundant number
+             {
+                return false;
+             }
+          }
+
+        // driver code
+        static void Main(string[] args)
+        {
+            int num;
+            bool res;
+            Console.WriteLine("Enter a number: ");
+            // reading data and converting into into int to store that in num variable
+            num = Convert.ToInt32(Console.ReadLine());
+            res = IsAbudant(num);
+            if (res)
+            {
+                Console.WriteLine($"{num} is an abundant number");
+            }
+            else
+            {
+                Console.WriteLine($"{num} is not an abundant number");
+            }
+        }
+    }
+}
+/*
+Input: Enter a number: 54
+Output: 54 is an abundant number
+Time complexity: O(N/2) where is the num given by user
+Space complexity: O(1)
+*/

algorithms/CSharp/test/Maths/AbundantTestUnit

@@ -0,0 +1,15 @@
+using NUnit.Framework;
+namespace Abundant.Test
+{
+    [TestFixture]
+    public class Testcase
+    {
+        [TestCase(54, true)]
+        [TestCase(5, false)]
+        public void PassNumber_ShouldGetExpectedResult(int num,bool expected)
+        {
+            var result = Abundant.Number.Abundant.IsAbudant(num);
+            Assert.AreEqual(expected, result);
+        }
+    }
+}