Added solution to problem 4

ProblemSelection.ts

@@ -27,11 +27,12 @@ import { Problem } from "./Problems/Problem";
 import { Problem1 } from "./Problems/Problem1";
 import { Problem2 } from "./Problems/Problem2";
 import { Problem3 } from "./Problems/Problem3";
+import { Problem4 } from "./Problems/Problem4";
 
 
 export class ProblemSelection{
 	//Holds the valid problem numbers
-	public static PROBLEM_NUMBERS: number[] = [1, 2, 3];
+	public static PROBLEM_NUMBERS: number[] = [1, 2, 3, 4];
 
 	//Returns the problem corresponding to the given problem number
 	public static getProblem(problemNumber: number): Problem{
@@ -40,6 +41,7 @@ export class ProblemSelection{
 			case 1 : problem = new Problem1(); break;
 			case 2 : problem = new Problem2(); break;
 			case 3 : problem = new Problem3(); break;
+			case 4 : problem = new Problem4(); break;
 		}
 		return problem;
 	}

Problems/Problem4.ts

@@ -0,0 +1,113 @@
+//ProjectEulerTS/Problems/Problem4.ts
+//Matthew Ellison
+// Created: 10-24-20
+//Modified: 10-24-20
+//Find the largest palindrome made from the product of two 3-digit numbers
+//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/typescriptClasses
+/*
+	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/>.
+*/
+
+
+import { Problem } from "./Problem";
+import { Unsolved } from "../Unsolved";
+
+
+export class Problem4 extends Problem{
+	//Variables
+	//Static variables
+	private static START_NUM: number = 100;	//The first number to be multiplied
+	private static END_NUM: number = 999;	//The last number to be multiplied
+	//Instance variables
+	private palindromes: number[];	//Holds all number that turn out to be palindromes
+
+	//Constructor
+	public constructor(){
+		super("Find the largest palindrome made from the product of two 3-digit numbers");
+	}
+	//Operational functions
+	//Solve the problem
+	public solve(): void{
+		//If the problem has already been solved do nothing and end the function
+		if(this.solved){
+			return;
+		}
+
+		//Start the timer
+		this.timer.start();
+
+		//Start at the first 3-digit number and check every one up to the last 3-digit number
+		for(let firstNum: number = Problem4.START_NUM;firstNum <= Problem4.END_NUM;++firstNum){
+			//You can start at the location of the first number because everything before that has already been tested. (100 * 101 == 101 * 100)
+			for(let secondNum = firstNum;secondNum < Problem4.END_NUM;++secondNum){
+				//Get the product
+				let product: number = firstNum * secondNum;
+				//Change the number into a string
+				let productString: string = product.toString();
+				//Reverse the string
+				let reverseString: string = productString.split("").reverse().join("");
+
+				//If the number and it's reverse are the same it is a palindrome so add it to the list
+				if(productString == reverseString){
+					this.palindromes.push(product);
+				}
+				//If it's not a palindrome ignore it and move to the next number
+			}
+		}
+
+		//Sort the palindromes so that the last one is the largest
+		this.palindromes = this.palindromes.sort((n1, n2) => n1 - n2);
+
+		//Stop the timer
+		this.timer.stop();
+
+		//Throw a flag to show the problem is solved
+		this.solved = true;
+	}
+
+	//Reset the problem so it can be run again
+	public reset(): void{
+		super.reset();
+		this.palindromes = [];
+	}
+	//Gets
+	//Returns the result of solving the problem
+	public getResult(): string{
+		if(!this.solved){
+			throw new Unsolved();
+		}
+		return `The largest palindrome is ${this.palindromes[this.palindromes.length - 1]}`;
+	}
+	//Returns the list of all palindromes
+	public getPalindromes(): number[]{
+		if(!this.solved){
+			throw new Unsolved();
+		}
+		return this.palindromes;
+	}
+	//Returns the largest palindrome
+	public getLargestPalindrome(): number{
+		if(!this.solved){
+			throw new Unsolved();
+		}
+		return this.palindromes[this.palindromes.length - 1];
+	}
+}
+
+/* Results:
+The largest palindrome is 906609
+It took an average of 121.130 milliseconds to run this problem through 100 iterations
+*/