In java, how would I find the nth Fibonacci number?

问题

Determining the Fibonacci sequence is easy enough to figure out:

int num = 0;
int num2 = 1;
int loop;
int fibonacci;
System.out.print(num2);
for (loop = 1; loop <= 10; loop ++)
{
    fibonacci = num + num2;
    num = num2;
    num2 = fibonacci;
    System.out.print(" " + fibonacci);
}

My problem lies with trying to pinpoint the value for a specified N. As in, If I want to find the 6th element in the sequence, which is 8, how would I find that number, and only that number?

回答1:

In your code, num starts as the 0^th Fibonacci number, and num1 as the 1^st. So to find the n^th, you have to iterate the step n times:

for (loop = 0; loop < n; loop ++)
{
    fibonacci = num + num2;
    num = num2;
    num2 = fibonacci;
}
System.out.print(num);

and only print it when you've finished.

When the loop counter loop has the value k, num holds the k^th Fibonacci number and num2 the (k+1)^th.

回答2:

To find the n'th digit, we need to know the length of the Fibonacci numbers. You can convert int to string using Java's Integer.toString(int) function. Using the string, one can then determine the length of the converted Fibonacci number.

EDIT: Removed code b/c likely hwk question

回答3:

int n=5;//position of the fibonacci number to find
int fibonacci=0,num=0,num2=1;
for(int loop=1;loop<n;loop++)
{
   fibonacci=num+num2;
   num=num2;
   num2=fibonacci;
}
System.out.println(num);

回答4:

import java.util.Scanner;
public class fibonacci{
public static void main(String[]args){
    Scanner i=new Scanner(System.in);
    String n=System.getProperty("line.separator");

    int count=0,x=0,y=1,sum;

    System.out.println("Enter a number:  ");
    int n=i.nextInt();

    for(count=0;count<n;count++){
        System.out.print(" "+ x);
        sum=x+y;
        x=y;
        y=sum;
    }
  }
}

回答5:

import acm.program.*;

public class FibonacciToN extends ConsoleProgram {

    public void run() {

        println("This program will display a table of Fibonacci numbers up to value n.");
        int n = readInt("Enter an integer for value n: ");
        int result = sequence(n);  

    }

    private int sequence(int n) {

        int a = 0;
        int b = 1;

        while (a < n) {  
            println(a); 
            a = a + b;
            b = a - b;
            }

        return a;
    }
}

来源：https://stackoverflow.com/questions/13021102/in-java-how-would-i-find-the-nth-fibonacci-number

标签

java

loops

for-loop

fibonacci