Java gcd gcd(long[] array)

Description

Computes the greatest absolute common divisor of an integer array.

License

Open Source License

Parameter

Parameter	Description
array	Input array

Return

The greatest absolute common divisor. By convention, gcd(0, 0) is equal to zero and gcd([]) is equal to one

Declaration

public static long gcd(long[] array) 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * Copyright (c) 2016 Pablo Pavon-Marino.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/lgpl.html
 *
 * Contributors:/*  w w  w  .  j  a va2  s .  c  o m*/
 *     Pablo Pavon-Marino - Jose-Luis Izquierdo-Zaragoza, up to version 0.3.1
 *     Pablo Pavon-Marino - from version 0.4.0 onwards
 ******************************************************************************/

import java.util.*;

public class Main {
    /**
     * Computes the greatest absolute common divisor of an integer array.
     *
     * @param array Input array
     * @return The greatest absolute common divisor. By convention, {@code gcd(0, 0)} is equal to zero and {@code gcd([])} is equal to one
     * 
     */
    public static long gcd(long[] array) {
        if (array.length == 0) {
            return 1;
        }

        long[] maxMinValue = maxMinValues(array);
        long minAbsValue = Math.min(Math.abs(maxMinValue[0]), Math.abs(maxMinValue[1]));

        for (long i = minAbsValue; i >= 1; i--) {
            int j;

            for (j = 0; j < array.length; ++j) {
                if (Math.abs(array[j]) % i != 0) {
                    break;
                }
            }

            if (j == array.length) {
                return i;
            }
        }

        return 1;
    }

    /**
     * Returns the maximum/minimum values of an input array.
     *
     * @param array Input array
     * @return Maximum/minimum values
     * 
     */
    public static long[] maxMinValues(long[] array) {
        if (array.length == 0) {
            throw new NoSuchElementException("Empty array");
        }

        long maxValue = array[0];
        long minValue = array[0];
        for (int i = 1; i < array.length; i++) {
            if (array[i] > maxValue) {
                maxValue = array[i];
            }

            if (array[i] < minValue) {
                minValue = array[i];
            }
        }

        return arrayOf(maxValue, minValue);
    }

    /**
     * Generates a {@code long[]} from comma-separated values.
     *
     * @param values Comma-separated {@code long} values
     * @return {@code long[]}
     * 
     */
    public static long[] arrayOf(long... values) {
        return values;
    }
}

Related

1. GCD(long a, long b)
2. gcd(long a, long b)
3. gcd(long u, long v)
4. gcd(long x, long y)
5. gcd(long x, long y)
6. gcd(long[] array)
7. gcd1(long given1, long given2)
8. GCDHelper(long a, long b)
9. gcdMultiple(int[] nums)