ConsecutiveFib.java

package main.java.kyu6;

/**
 * 6 kyu - Product of consecutive Fib numbers
 *
 * https://www.codewars.com/kata/5541f58a944b85ce6d00006a
 *
 * Details:
 *
 * The Fibonacci numbers are the numbers in the following integer sequence (Fn):
 *     0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, ...
 *
 * such as
 *     F(n) = F(n-1) + F(n-2) with F(0) = 0 and F(1) = 1.
 *
 * Given a number, say prod (for product), we search two Fibonacci numbers F(n) and F(n+1)
 * verifying
 *     F(n) * F(n+1) = prod.
 *
 * Your function productFib takes an integer (prod) and returns an array:
 * [F(n), F(n+1), true] or {F(n), F(n+1), 1} or (F(n), F(n+1), True)
 *
 * depending on the language if
 * F(n) * F(n+1) = prod.
 *
 * If you don't find two consecutive F(m) verifying F(m) * F(m+1) = prod you will return
 * [F(m), F(m+1), false] or {F(n), F(n+1), 0} or (F(n), F(n+1), False)
 *
 * F(m) being the smallest one such as F(m) * F(m+1) > prod.
 */

public class ConsecutiveFib {
    public static long[] productFib(long prod) {
        long a = 0;
        long b = 1;

        while (a * b <= prod) {
            if ((a * b) == prod) {
                return new long[]{a, b, 1};
            }

            final long buff = a;
            a = b;
            b += buff;
        }
        return new long[]{a, b, 0};
    }
}