java - 使用迭代器递减斐波那契数

Question

所以我的代码基本上是有效的，至少我的预期是这样。但我的问题是我的斐波那契数应该是下降而不是上升。我为此苦苦挣扎的原因是因为起始数字是用户输入，所以与升序不同，我每次都不知道第一步是什么。我考虑只是将整数加载到数组中，对它们进行排序和打印，但我觉得这违背了迭代器的目的......有什么想法吗？这是我的代码：

import java.util.Iterator;
import java.util.Scanner;
import java.text.SimpleDateFormat;
import java.util.*;
import java.text.DateFormat;

public class Conversion1
{

    public static void main(String[] args)
    {

        Scanner scanner = new Scanner(System.in);

        int choice = 0;
        int prime = 0, p = 0;
        int fib = 0, f = 0;
        long pTime = 0;
        long fTime = 0;
        long pETime = 0;
        long fETime = 0;
        int ff[];
        long start = System.currentTimeMillis();

        while (choice != 3)
        {
            System.out.println("Enter 1 or 2 to print out Fibonacci or Prime number iterator or enter 3 to exit.");
            System.out.println("1 - Fibonacci Number Iterator");
            System.out.println("2 - Prime Number Iterator");
            System.out.println("3 - Exit");
            choice = scanner.nextInt();
            switch (choice)
            {
                case 1:
                    fTime += System.currentTimeMillis();
                    System.out.println("Enter the Max value");
                    int maxInt2 = scanner.nextInt();
                    ff = new int[maxInt2];
                    Iterator iterator = new FibonacciIterator(maxInt2);
                    while (iterator.hasNext())
                    {
                        ff[f] = (int) iterator.next();
                        f++;
                    }
                    for (int i = 0; i < f; i++)
                        System.out.println(ff[i]);
                    fETime += System.currentTimeMillis();
                    fib++;
                    break;

                case 2:
                    pTime += System.currentTimeMillis();
                    System.out.println("Enter the Max value");
                    int maxInt = scanner.nextInt();
                    Iterator iterator2 = new PrimeIterator(maxInt);

                    while (iterator2.hasNext())
                    {
                        System.out.println(iterator2.next());
                        p++;
                    }

                    System.out.println("\n");
                    pETime += System.currentTimeMillis();
                    prime++;
                    break;

                case 3:
                    long pFinal = pETime - pTime;
                    long fFinal = fETime - fTime;
                    double fseconds = ((fFinal / 1000) % 60);
                    double pseconds = ((pFinal / 1000) % 60);
                    System.out.println("\n");
                    System.out.println(fib + " Fibonacci commands yielding " + f + " individual outputs requiring "
                        + fseconds + " seconds.");
                    System.out.println("\n");
                    System.out.println(prime + " Prime commands yielding " + p + " individual outputs requiring " + pseconds
                        + " seconds.");
                    System.out.println("\n");
                    long end = System.currentTimeMillis();
                    DateFormat df = new SimpleDateFormat("HH':'mm':'ss");
                    System.out.println("Program started at " + df.format(new Date(start)) + " and terminated at: "
                        + df.format(new Date(end)));
                    System.out.println("\n");
                    System.out.println("Program Ended");
                    System.out.println("\n");
                    break;

                default:

                    System.out.println("Invalid Input");

            }

        }
    }

    static class PrimeIterator implements java.util.Iterator
    {
        private int limit = 0;
        private int current;
        private int a_number;

        public PrimeIterator(int current)
        {
            this.current = current;
        }

        @Override
        public Integer next()
        {
            return current;
        }

        static boolean isPrime(int number)
        {
            for (int divisor = 2; divisor < number; divisor++)
                if (number % divisor == 0)
                    return false;

            return true;

        }

        @Override
        public boolean hasNext()
        {
            current--;

            while (true)
            {
                if (isPrime(current))
                    break;

                current--;
            }

            if (current <= limit)

                return false;

            else

                return true;

        }
    }

    static class FibonacciIterator implements java.util.Iterator
    {
        private int limit;
        private int current = 1;// -1,1,0,1,1,2,3,5
        private int prev = -1;

        public FibonacciIterator(int limit)
        {    
            this.limit = limit;
        }

        @Override
        public Integer next()
        {
            return current;
        }

        @Override
        public boolean hasNext()
        {
            int temp = current;
            current = current + prev;// -1+1=0
            prev = temp;

            if (current >= limit)
                return false;

            else

                return true;

        }

        @Override
        public void remove()
        {
            throw new UnsupportedOperationException("Method not supported");
        }
    }
}

标签： javaiteratorfibonacci

Answer 1

如果你必须颠倒顺序，你能不只是翻转捕获的斐波那契值的顺序吗？

                for (int i = f - 1; i >= 0; i--)
                    System.out.println(ff[i]);

与您从索引 0 开始的位置相反。

                for (int i = 0; i < f; i++)
                    System.out.println(ff[i]);