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78 lines
2.6 KiB
Java
78 lines
2.6 KiB
Java
//ProjectEuler/Java/Problem15.java
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//Matthew Ellison
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// Created: 03-04-19
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//Modified: 03-28-19
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//How many routes from the top left corner to the bottom right corner are there through a 20×20 grid if you can only move right and down?
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//Unless otherwise listed all non-standard includes are my own creation and available from https://bibucket.org/Mattrixwv/JavaClasses
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//This program has not been tested fully and has not even been run to completion because of the long time it takes to run
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/*
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Copyright (C) 2019 Matthew Ellison
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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import mattrixwv.Stopwatch;
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public class Problem15{
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private static final Integer WIDTH = 20;
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private static final Integer LENGTH = 20;
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public static void main(String[] argv){
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Stopwatch timer = new Stopwatch(); //Used to determine the algorithm's run time
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//Setup the rest of the variables
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Long numOfRoutes = 0L; //The number of routes from 0, 0, to 20, 20
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Integer currentX = 0; //The current x location on the grid
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Integer currentY = 0; //The current y location on the grid
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//Start the timer
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timer.start();
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//We write this as a recursive function
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//When in a location it always moves right first, then down
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move(currentX, currentY, numOfRoutes);
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//Stop the timer
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timer.stop();
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//Print the results
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System.out.println("The number of routes is " + numOfRoutes.toString());
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System.out.println("It took " + timer.getStr() + " to run this algorithm");
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}
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//This function acts as a handler for moving the position on the grid and counting the distance
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//It moves right first, then down
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private static void move(Integer currentX, Integer currentY, Long numOfRoutes){
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//Check if you are at the end and act accordingly
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if((currentX == WIDTH) && (currentY == LENGTH)){
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++numOfRoutes;
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return;
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}
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//Move right if possible
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if(currentX < WIDTH){
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move(currentX + 1, currentY, numOfRoutes);
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}
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//Move down if possible
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if(currentY < LENGTH){
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move(currentX, currentY + 1, numOfRoutes);
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}
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}
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}
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/* Results:
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*/
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