From b72b0d2e0cb5a63096b14c4a041b847f07bcb67c Mon Sep 17 00:00:00 2001
From: Mattrixwv <m_ellison@ymail.com>
Date: Fri, 28 May 2021 14:12:45 -0400
Subject: [PATCH] Added solution to problem 31

---
 ProblemSelection.ts   |   4 +-
 Problems/Problem31.ts | 102 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 105 insertions(+), 1 deletion(-)
 create mode 100644 Problems/Problem31.ts

diff --git a/ProblemSelection.ts b/ProblemSelection.ts
index 556f9fa..4e4c94b 100644
--- a/ProblemSelection.ts
+++ b/ProblemSelection.ts
@@ -54,12 +54,13 @@ import { Problem27 } from "./Problems/Problem27";
 import { Problem28 } from "./Problems/Problem28";
 import { Problem29 } from "./Problems/Problem29";
 import { Problem30 } from "./Problems/Problem30";
+import { Problem31 } from "./Problems/Problem31";
 
 
 export class ProblemSelection{
 	//Holds the valid problem numbers
 	public static PROBLEM_NUMBERS: number[] = [  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
-												21, 22, 23, 24, 25, 26, 27, 28, 29, 30];
+												21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31];
 
 	//Returns the problem corresponding to the given problem number
 	public static getProblem(problemNumber: number): Problem{
@@ -95,6 +96,7 @@ export class ProblemSelection{
 			case 28: problem = new Problem28(); break;
 			case 29: problem = new Problem29(); break;
 			case 30: problem = new Problem30(); break;
+			case 31: problem = new Problem31(); break;
 		}
 		return problem;
 	}
diff --git a/Problems/Problem31.ts b/Problems/Problem31.ts
new file mode 100644
index 0000000..7007001
--- /dev/null
+++ b/Problems/Problem31.ts
@@ -0,0 +1,102 @@
+//ProjectEulerTS/Problems/Problem31.ts
+//Matthew Ellison
+// Created: 05-28-21
+//Modified: 05-28-21
+//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/typescriptClasses
+/*
+	Copyright (C) 2021  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 { Unsolved } from "../Unsolved";
+import { Problem } from "./Problem";
+
+
+export class Problem31 extends Problem{
+	//Variables
+	//Static variables
+	private static DESIRED_VALUE: number = 200;	//The value of voins we want
+	//Instance variables
+	private permutations: number;	//The number of permutations that are found
+
+	//Functions
+	//Constructor
+	public constructor(){
+		super("How many different ways can 2 pounds be made using any number of coins?");
+		this.permutations = 0;
+	}
+	//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 with 200p and remove the necessary coins with each loop
+		for(let pound2 = Problem31.DESIRED_VALUE;pound2 >= 0;pound2 -= 200){
+			for(let pound1 = pound2;pound1 >= 0;pound1 -= 100){
+				for(let pence50 = pound1;pence50 >= 0;pence50 -= 50){
+					for(let pence20 = pence50;pence20 >= 0;pence20 -= 20){
+						for(let pence10 = pence20;pence10 >= 0;pence10 -= 10){
+							for(let pence5 = pence10;pence5 >= 0;pence5 -= 5){
+								for(let pence2 = pence5;pence2 >= 0;pence2 -= 2){
+									++this.permutations;
+								}
+							}
+						}
+					}
+				}
+			}
+		}
+
+		//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.permutations = 0;
+	}
+	//Gets
+	//Returns the result of solving the proble
+	public getResult(): string{
+		if(!this.solved){
+			throw new Unsolved();
+		}
+		return `There are ${this.permutations} ways to make 2 pounds with the given denominations of coins`;
+	}
+	//Returns the number of correct permutations of the coins
+	public getPermutations(): number{
+		//If the problem hasn't been solved throw an exception
+		if(!this.solved){
+			throw new Unsolved();
+		}
+		return this.permutations;
+	}
+}
+
+/* Results:
+There are 73682 ways to make 2 pounds with the given denominations of coins
+It took an average of 197.293 microseconds to run this problem through 100 iterations
+*/