96 lines
2.6 KiB
Java
96 lines
2.6 KiB
Java
//JavaClasses/src/main/java/mattrixwv/HexagonalNumberGenerator.java
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//Matthew Ellison
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// Created: 08-20-22
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//Modified: 08-11-24
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//This class generates hexagonal numbers
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/*
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Copyright (C) 2024 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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package com.mattrixwv.generators;
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import java.util.Iterator;
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import java.util.NoSuchElementException;
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/**
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* A generator for hexagonal numbers, which implements the {@link Iterator} interface.
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*
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* <p>
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* Hexagonal numbers are figurate numbers that represent hexagons. The n-th hexagonal number is given by
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* the formula: H(n) = 2n^2 - n.
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* </p>
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*
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* <p>
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* This generator allows iteration over hexagonal numbers starting from the first.
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* </p>
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*/
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public class HexagonalNumberGenerator implements Iterator<Long>{
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/**
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* The number to generate the next hexagonal number from.
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*/
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protected long num;
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/**
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* Constructs a new HexagonalNumberGenerator starting from the first hexagonal number.
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*/
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public HexagonalNumberGenerator(){
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num = 1L;
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}
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/**
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* Checks if there is a next hexagonal number that can be generated without overflow.
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*
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* @return {@code true} if the next hexagonal number can be generated, {@code false} otherwise
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*/
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@Override
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public boolean hasNext(){
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return (2 * num * num) > num;
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}
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/**
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* Returns the next hexagonal number.
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*
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* @return the next hexagonal number
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* @throws NoSuchElementException if the next hexagonal number would cause overflow
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*/
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@Override
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public Long next(){
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//If the number will result in an overflow throw an exception
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if(!hasNext()){
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throw new NoSuchElementException("Number overflow");
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}
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//Generate and return the hexagonal number
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Long hexNum = ((2L * num * num) - num);
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++num;
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return hexNum;
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}
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/**
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* Checks if a given number is a hexagonal number.
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*
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* @param x the number to check
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* @return {@code true} if the number is hexagonal, {@code false} otherwise
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*/
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public static boolean isHexagonal(Long x){
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Long n = Math.round((Math.sqrt(1.0D + (8L * x)) + 1L) / 4L);
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return ((2L * n * n) - n) == x;
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}
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}
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