Added solution to problem 28

ProjectEulerCS/ProblemSelection.cs

@@ -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,
-				 20, 21, 22, 23, 24, 25, 26, 27, 67};
+				 20, 21, 22, 23, 24, 25, 26, 27, 28, 67};
 		public static System.Collections.Generic.List<int> PROBLEM_NUMBERS{
 			get { return _PROBLEM_NUMBERS; }
 		}
@@ -68,6 +68,7 @@ namespace ProjectEulerCS{
 				case 25: problem = new Problem25(); break;
 				case 26: problem = new Problem26(); break;
 				case 27: problem = new Problem27(); break;
+				case 28: problem = new Problem28(); break;
 				case 67: problem = new Problem67(); break;
 			}
 			return problem;

ProjectEulerCS/Problems/Problem28.cs

@@ -0,0 +1,171 @@
+//ProjectEuler/ProjectEulerCS/src/Problems/Problem28.cs
+//Matthew Ellison
+// Created: 09-21-20
+//Modified: 09-21-20
+//What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed by starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral
+//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.Collections.Generic;
+
+
+namespace ProjectEulerCS.Problems{
+	public class Problem28 : Problem{
+		//Variables
+		//Static variables
+		private static List<List<int>> grid;	//Holds the grid that we will be filling and searching
+		//Instance variables
+		private int sumOfDiagonals;	//Holds the sum of the diagonals of the grid
+		public List<List<int>> Grid{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return grid;
+			}
+		}
+		public int Sum{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return sumOfDiagonals;
+			}
+		}
+		public override string Result{
+			get{
+				if(!solved){
+					throw new Unsolved();
+				}
+				return $"The sum of the diagonals in the given grid is {sumOfDiagonals}";
+			}
+		}
+
+		//Functions
+		//Constructor
+		public Problem28() : base("What is the sum of the numbers on the diagonals in a 1001 by 1001 spiral formed by starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral"){
+			sumOfDiagonals = 0;
+		}
+		//Operational functions
+		//Sets up the grid
+		private void SetupGrid(){
+			grid = new List<List<int>>();
+			//Fill the grid with 0's
+			for(int cnt = 0;cnt < 1001;++cnt){
+				//Add a blank List
+				grid.Add(new List<int>());
+				for(int cnt2 = 0;cnt2 < 1001;++cnt2){
+					grid[cnt].Add(0);
+				}
+			}
+
+			bool finalLocation = false;	//A flag to indicate if the final location to be filled has been reached
+			//Set the number that is going to be put at each location
+			int currentNum = 1;
+			//Start with the middle location and set it correctly and advance the tracker to the next number
+			int xLocation = 500;
+			int yLocation = 500;
+			grid[yLocation][xLocation] = currentNum++;
+			//Move right the first time
+			++xLocation;
+			//Move in a circular pattern until you reach the final location
+			while(!finalLocation){
+				//Move down until you reach a blank location on the left
+				while(grid[yLocation][xLocation - 1] != 0){
+					grid[yLocation][xLocation] = currentNum++;
+					++yLocation;
+				}
+
+				//Move left until you reach a blank location above
+				while(grid[yLocation - 1][xLocation] != 0){
+					grid[yLocation][xLocation] = currentNum++;
+					--xLocation;
+				}
+
+				//Move up until you reach a blank location to the right
+				while(grid[yLocation][xLocation + 1] != 0){
+					grid[yLocation][xLocation] = currentNum++;
+					--yLocation;
+				}
+
+				//Move right until you reach a blank location below
+				while(grid[yLocation + 1][xLocation] != 0){
+					grid[yLocation][xLocation] = currentNum++;
+					++xLocation;
+					//Check if you are at the final location and break the loop if you are
+					if(xLocation == grid.Count){
+						finalLocation = true;
+						break;
+					}
+				}
+			}
+		}
+		//Finds the sum of the diagonals in the grid
+		private void FindSum(){
+			//Start at the top corners and work your way down moving toward the opposite side
+			int leftSide = 0;
+			int rightSide = grid.Count - 1;
+			int row = 0;
+			while(row < grid.Count){
+				//This ensures the middle location is only counted once
+				if(leftSide == rightSide){
+					sumOfDiagonals += grid[row][leftSide];
+				}
+				else{
+					sumOfDiagonals += grid[row][leftSide];
+					sumOfDiagonals += grid[row][rightSide];
+				}
+				++row;
+				++leftSide;
+				--rightSide;
+			}
+		}
+		//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();
+
+			//Setup the grid
+			SetupGrid();
+			//Find the sum of the diagonals in the grid
+			FindSum();
+
+			//Stop the timer
+			timer.Stop();
+
+			//Throw a flag to show the problem is solved
+			solved = true;
+		}
+		//Reset the problem so it can be run again
+		public override void Reset(){
+			base.Reset();
+			sumOfDiagonals = 0;
+		}
+	}
+}
+
+/* Results:
+The sum of the diagonals in the given grid is 669171001
+It took an average of 7.735 milliseconds to run this problem through 100 iterations
+*/