Java Program to Generate Fibonacci Series in Reverse Order

The Fibonacci series is defined as follows:

1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …

This can be represented as an array where: a[0] = 1, a[1] = 1, a[2] = 2, …, a[n] = a[n-1] + a[n-2].

This program, named 'TestFibonacci.java', reads two non-negative numbers (n and d) from the console using System.in. The program then outputs d elements of the series, starting from the n-th element, in reverse order to the console using System.out. You can assume that the input numbers are no larger than 100,000.

import java.util.*;

public class TestFibonacci {

    static Scanner input = new Scanner(System.in);

    // here is the function you need to implement
    public static void parse_line(int n, int d) {
        int[] f = new int[n + d];
        f[0] = 1;
        f[1] = 1;
        for (int i = 2; i < n + d; i++) {
            f[i] = f[i - 1] + f[i - 2];
        }

        int count = 0; // 计数器变量
        for (int i = n - 1; i >= n - d; i--) {
            System.out.print(f[i]);
            count++;
            if (count < d) {
                System.out.print(", "); // 在最后一个元素之后停止添加逗号
            }
        }
    }

    public static void main(String[] args) throws Exception {
        int line_number = Integer.parseInt(input.nextLine());
        for (int i = 0; i < line_number; i++) {
            String s = input.nextLine();
            String t[] = s.split(", ");
            int n = Integer.parseInt(t[0]);
            int d = Integer.parseInt(t[1]);
            TestFibonacci.parse_line(n, d);
            System.out.println();
        }
    }
}

Explanation:

Input: The program first reads the number of input lines (line_number) followed by line_number lines containing two integers separated by a comma and space (, ). These integers represent n and d respectively.
Fibonacci Calculation: The parse_line function calculates the Fibonacci series up to n + d elements. This is done by iterating from i = 2 to n + d, adding the previous two elements (f[i-1] and f[i-2]) to get the current element (f[i]).
Reverse Order Output: The program then iterates from the n-1th element to the n-dth element. For each element, the program prints its value and increments a counter variable (count). If the counter is less than d, the program prints a comma and space (, ) to separate the elements. This ensures that there is no comma after the last element.

Example Usage:

Input:

2
5, 3
10, 2

Output:

8, 5, 3
55, 34

This program demonstrates a simple yet efficient way to generate and manipulate Fibonacci sequences in Java. You can easily modify this code to adapt it to various scenarios involving Fibonacci sequences.

Java Program to Generate Fibonacci Series in Reverse Order