ProjectEulerJava/src/main/java/com/mattrixwv/project_euler/problems/Problem11.java

//ProjectEulerJava/src/main/java/mattrixwv/ProjectEuler/Problems/Problem11.java
//Matthew Ellison
// Created: 03-03-19
//Modified: 06-27-23
//What is the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the 20×20 grid?
//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/JavaClasses
/*
	Copyright (C) 2023  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/>.
*/
package com.mattrixwv.project_euler.problems;


import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.security.InvalidParameterException;
import java.util.ArrayList;
import java.util.List;

import com.mattrixwv.ArrayAlgorithms;


public class Problem11 extends Problem{
	//Variables
	//Static variables
	//This is the grid of numbers that we will be working with
	protected static String fileName = "files/Problem11Grid.txt";
	protected static ArrayList<List<Integer>> grid;
	//Instance variables
	protected List<Integer> greatestProduct;	//Holds the largest product we have found so far

	//Functions
	//Constructor
	public Problem11(){
		super("What is the greatest product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the 20×20 grid?");
		greatestProduct = new ArrayList<>();
	}
	//Operational functions
	//Read numbers from file into grid
	private static void readFile(){
		if(grid != null){
			return;
		}
		File file = new File(fileName);
		if(file.exists()){
			try{
				List<String> lines = Files.readAllLines(file.toPath());
				grid = new ArrayList<>();
				for(String line : lines){
					ArrayList<Integer> row = new ArrayList<>();
					for(String num : line.split(" ")){
						row.add(Integer.parseInt(num));
					}
					grid.add(row);
				}
			}
			catch(IOException error){
				throw new InvalidParameterException("Error reading file", error);
			}
		}
		else{
			throw new InvalidParameterException("Error opening file");
		}
	}
	//Solve the problem
	@Override
	public void solve(){
		//If the problem has already been solved do nothing and end the function
		if(solved){
			return;
		}

		//Holds the numbers we are currently working on
		ArrayList<Integer> currentProduct = new ArrayList<>();

		//Make sure all elements have at least 4 elements
		for(int cnt = 0;cnt < 4;++cnt){
			greatestProduct.add(0);
			currentProduct.add(0);
		}

		//Read the file into the number
		readFile();

		//Start the timer
		timer.start();


		//Loop through every row and column
		for(int row = 0;row < grid.size();++row){
			for(int col = 0;col < grid.get(row).size();++col){
				//Directional booleans to show whether you can move a certain direction
				boolean left = false;
				boolean right = false;
				boolean down = false;

				//Check which direction you will be able to move
				if((col - 3) >= 1){
					left = true;
				}
				if((col + 3) < grid.get(row).size()){
					right = true;
				}
				if((row + 3) < 20){
					down = true;
				}

				//Check the direction you are able to go
				//Right
				if(right){
					checkRight(currentProduct, row, col);
				}
				//Down
				if(down){
					checkDown(currentProduct, row, col);
				}
				//LeftDown
				if(left && down){
					checkLeftDown(currentProduct, row, col);
				}
				//RightDown
				if(right && down){
					checkRightDown(currentProduct, row, col);
				}
			}
		}


		//Stop the timer
		timer.stop();

		//Throw a flag to show the problem is solved
		solved = true;
	}
	//Check to the right of the current location
	private void checkRight(ArrayList<Integer> currentProduct, int row, int col){
		//Fill the product
		currentProduct.set(0, grid.get(row).get(col));
		currentProduct.set(1, grid.get(row).get(col + 1));
		currentProduct.set(2, grid.get(row).get(col + 2));
		currentProduct.set(3, grid.get(row).get(col + 3));

		//If the current number's product is greater than the greatest product replace it
		if(ArrayAlgorithms.getProd(currentProduct) > ArrayAlgorithms.getProd(greatestProduct)){
			greatestProduct.set(0, currentProduct.get(0));
			greatestProduct.set(1, currentProduct.get(1));
			greatestProduct.set(2, currentProduct.get(2));
			greatestProduct.set(3, currentProduct.get(3));
		}
	}
	//Check below the current location
	private void checkDown(ArrayList<Integer> currentProduct, int row, int col){
		//Fill the product
		currentProduct.set(0, grid.get(row).get(col));
		currentProduct.set(1, grid.get(row + 1).get(col));
		currentProduct.set(2, grid.get(row + 2).get(col));
		currentProduct.set(3, grid.get(row + 3).get(col));

		//If the current number's product is greater than the greatest product replace it
		if(ArrayAlgorithms.getProd(currentProduct) > ArrayAlgorithms.getProd(greatestProduct)){
			greatestProduct.set(0, currentProduct.get(0));
			greatestProduct.set(1, currentProduct.get(1));
			greatestProduct.set(2, currentProduct.get(2));
			greatestProduct.set(3, currentProduct.get(3));
		}
	}
	//Check the left-down diagonal from the current location
	private void checkLeftDown(ArrayList<Integer> currentProduct, int row, int col){
		//Fill the product
		currentProduct.set(0, grid.get(row).get(col));
		currentProduct.set(1, grid.get(row + 1).get(col - 1));
		currentProduct.set(2, grid.get(row + 2).get(col - 2));
		currentProduct.set(3, grid.get(row + 3).get(col - 3));

		//If the current number's product is greater than the greatest product replace it
		if(ArrayAlgorithms.getProd(currentProduct) > ArrayAlgorithms.getProd(greatestProduct)){
			greatestProduct.set(0, currentProduct.get(0));
			greatestProduct.set(1, currentProduct.get(1));
			greatestProduct.set(2, currentProduct.get(2));
			greatestProduct.set(3, currentProduct.get(3));
		}
	}
	//Check the right-down diagonal from the current location
	private void checkRightDown(ArrayList<Integer> currentProduct, int row, int col){
		//Fill the product
		currentProduct.set(0, grid.get(row).get(col));
		currentProduct.set(1, grid.get(row + 1).get(col + 1));
		currentProduct.set(1, grid.get(row + 2).get(col + 2));
		currentProduct.set(1, grid.get(row + 3).get(col + 3));

		//If the current number's product is greater than the greatest product replace it
		if(ArrayAlgorithms.getProd(currentProduct) > ArrayAlgorithms.getProd(greatestProduct)){
			greatestProduct.set(0, currentProduct.get(0));
			greatestProduct.set(1, currentProduct.get(1));
			greatestProduct.set(2, currentProduct.get(2));
			greatestProduct.set(3, currentProduct.get(3));
		}
	}
	//Reset the problem so it can be run again
	@Override
	public void reset(){
		super.reset();
		greatestProduct.clear();
	}
	//Gets
	//Returns the result of solving the problem
	@Override
	public String getResult(){
		solvedCheck("result");
		return String.format("The greatest product of 4 numbers in a line is %d%nThe numbers are %s", ArrayAlgorithms.getProd(greatestProduct), greatestProduct.toString());
	}
	//Returns the numbers that were being searched
	public List<Integer> getNumbers(){
		solvedCheck("numbers");
		return greatestProduct;
	}
	//Returns the product that was requested
	public int getProduct(){
		solvedCheck("product of the numbers");
		return ArrayAlgorithms.getProd(greatestProduct);
	}
}


/* Results:
The greatest product of 4 numbers in a line is 70600674
The numbers are [89, 94, 97, 87]
It took an average of 301.209 microseconds to run this problem through 100 iterations
*/