Added solution to problem 31

Source/Problem31.cpp

@@ -0,0 +1,86 @@
+//ProjectEuler/C++/Source/Problem31.cpp
+//Matthew Ellison
+// Created: 06-19-20
+//Modified: 06-19-20
+//How many different ways can £2 be made using any number of coins?
+//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/myClasses
+/*
+	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/>.
+*/
+
+
+#include <string>
+#include <sstream>
+#include <vector>
+#include "../Headers/Problem31.hpp"
+
+
+int Problem31::desiredValue = 200;
+
+Problem31::Problem31() : Problem("How many different ways can 2 pounds be made using any number of coins?"){
+	permutations = 0;
+}
+
+void Problem31::solve(){
+	//If the problem has alread been solved do nothing and end the function
+	if(solved){
+		return;
+	}
+
+	//Start the timer
+	timer.start();
+
+	//Start with 200p and remove the necessary coins with each loop
+	for(int pound2 = desiredValue;pound2 >= 0;pound2 -= 200){
+		for(int pound1 = pound2;pound1 >= 0;pound1 -= 100){
+			for(int pence50 = pound1;pence50 >= 0;pence50 -= 50){
+				for(int pence20 = pence50;pence20 >= 0;pence20 -= 20){
+					for(int pence10 = pence20;pence10 >= 0;pence10 -= 10){
+						for(int pence5 = pence10;pence5 >= 0;pence5 -= 5){
+							for (int pence2 = pence5; pence2 >= 0; pence2 -= 2){
+								++permutations;
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
+
+	//Stop the timer
+	timer.stop();
+
+	//Throw a flag to show the problem is solved
+	solved = true;
+}
+
+std::string Problem31::getString() const{
+	//If the problem hasn't been solved throw an exception
+	if(!solved){
+		throw unsolved();
+	}
+
+	std::stringstream results;
+	results << "There are " << permutations << " ways to make 2 pounds with the given denominations of coins";
+
+	return results.str();
+}
+
+//Returns the number of correct permutations of the coins
+int Problem31::getPermutations() const{
+	return permutations;
+}