Added solution to problem 20

ProjectEulerCS/ProblemSelection.cs

@@ -1,7 +1,7 @@
 //ProjectEuler/ProjectEulerCS/src/ProblemSelection.cs
 //Matthew Ellison
 // Created: 08-21-20
-//Modified: 08-24-20
+//Modified: 08-27-20
 //This class holds all of the functions needed to handle a problem
 /*
 	Copyright (C) 2020  Matthew Ellison
@@ -32,7 +32,7 @@ namespace ProjectEulerCS{
 		private static readonly List<int> _PROBLEM_NUMBERS = new List<int>()
 				{ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9,
 				 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
-				 67};
+				 20, 67};
 		public static System.Collections.Generic.List<int> PROBLEM_NUMBERS{
 			get { return _PROBLEM_NUMBERS; }
 		}
@@ -60,6 +60,7 @@ namespace ProjectEulerCS{
 				case 17: problem = new Problem17(); break;
 				case 18: problem = new Problem18(); break;
 				case 19: problem = new Problem19(); break;
+				case 20: problem = new Problem20(); break;
 				case 67: problem = new Problem67(); break;
 			}
 			return problem;

ProjectEulerCS/Problems/Problem20.cs

@@ -0,0 +1,113 @@
+//ProjectEuler/ProjectEulerCS/src/Problems/Problem19.cs
+//Matthew Ellison
+// Created: 08-27-20
+//Modified: 08-27-20
+//What is the sum of the digits of 100!?
+//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/CSClasses
+/*
+	Copyright (C) 2020  Matthew Ellison
+
+	This program is free software: you can redistribute it and/or modify
+	it under the terms of the GNU Lesser General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	This program is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU Lesser General Public License for more details.
+
+	You should have received a copy of the GNU Lesser General Public License
+	along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+
+using System.Numerics;
+
+
+namespace ProjectEulerCS.Problems{
+	public class Problem20 : Problem{
+		//Variables
+		//Static variables
+		private const int TOP_NUM = 100;	//The largest number that will be multiplied
+		//Instance variables
+		private BigInteger num;	//Holds the number 100!
+		public BigInteger Number{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return num;
+			}
+		}
+		public string NumberString{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return num.ToString();
+			}
+		}
+		private long sum;	//THe sum of the digits of num
+		public long Sum{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return sum;
+			}
+		}
+
+		//Functions
+		//Constructor
+		public Problem20() : base("What is the sum of the digits of 100!?"){
+			num = 1;
+			sum = 0;
+		}
+		//Operational functions
+		//Solve the problem
+		public override void Solve(){
+			//If the problem has already been solved do nothing and end the function
+			if(solved){
+				return;
+			}
+
+			//Start the timer
+			timer.Start();
+
+			//Run through every number from 1 to 100 and multiply it by the current num to generate 100!
+			for(int cnt = TOP_NUM;cnt > 1;--cnt){
+				num *= cnt;
+			}
+
+			//Get a string of the number because it is easier to pull apart the individual characters 
+			string numString = num.ToString();
+			//Run through every character in the string, convert it back to an integer and add it to the running sum
+			for(int cnt = 0;cnt < numString.Length;++cnt){
+				char digit = numString[cnt];
+				sum += (long)char.GetNumericValue(digit);
+			}
+
+			//Stop the timer
+			timer.Stop();
+
+			//Throw a flag to show the problem is solved
+			solved = true;
+
+			//Save the results
+			_result = TOP_NUM + "! = " + num + "\nThe sum of the digits is: " + sum;
+		}
+		//Reset the problem so it can be run again
+		public override void Reset(){
+			base.Reset();
+			num = 1;
+			sum = 0;
+		}
+	}
+}
+
+/* Results:
+100! = 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000
+The sum of the digits is: 648
+It took an average of 11.740 microseconds to run this problem through 100 iterations
+*/