如何确定最大的斐波那契数

Question

我被要求确定可以在我的系统上显示的最大的斐波纳契数,我想知道如何做到这一点..

这是我的简单应用程序,它决定了第n个斐波纳契数

import java.util.Scanner;

public class FibonacciTest
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        System.out.printf("please enter the nth fibonacci number: ");

        int n = input.nextInt();
        System.out.printf("%d\n", fibonacci(n));

    }// end main

    public static int fibonacci(int n)
    {
        // determines nth fibonacci number
        int fib = 1;
        int temp = 0;

        if (n == 1)
            return 0;

        else
        {
            for (int i = 2; i < n; i++)
            {
                int last = fib;
                fib += temp;
                temp = last;
            }
            return fib;
        }

    }// end fibonacci
}

Answer 1

确定可以在我的系统上显示的最大斐波那契数

为此,您需要使用BigInteger

运行此操作直到您的应用程序停止,因为您的资源已用完.

public static void main(String... args) {
    BigInteger a = BigInteger.ONE;
    BigInteger b = BigInteger.ONE;
    String last = null;
    try {
        for (long count = 1; ; count++) {
            BigInteger c = a.add(b);
            last = c.toString();
            a = b;
            b = c;
            if (count % 10000 == 0)
                System.out.println("... " + count);
        }
    } catch (Throwable e) {
        System.out.println("The largest value which was calculated was");
        System.out.println(last);
    }
}

我会首先尝试使用少量内存,例如 -mx16m

更新:即使限制为16 MB,它也计算了13K项并仍在运行.

Answer 2

intJava中最大的斐波纳契数:

public class FibonacciTest
{
    public static void main(String[] args)
    {
        System.out.printf("%d\n", largestFibonacciInt());
    }

    public static int largestFibonacciInt()
    {
        int temp;
        int last = 1;
        int fib = 1;

        while (fib + last > fib) {
            temp = fib;
            fib += last;
            last = temp;
        }

        return fib;
    }
}

您也可以long通过简单地替换所有出现的内容来执行此操作int.