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I am looking for a clear explanation to my question (NOT looking for code), but if a bit of code helps to explain yourself, then please do.. thank you :)

Question:

-using Java

-Main class asks user for an integer input (fibonacci N term), then proceeds to calculate all the fibonacci numbers, in order, until it reaches that term.

-everything is stored into a single arraylists, of type integer. (Each digit is broken up and stored in its own index, so it is its own "element", so to speak.)

For example, i am aiming for it to go something like this:

"Please enter an N fibonacci term:"

10

At this point now, internally, I have stored the 2 base cases in an arraylist, that look like this:

ArrayList: [1, 1]

Now, I am trying to make my arraylist look like this, after user input:

[1, 1, 2, 3, 5, 8, 1, 3, 2, 1, 3, 4, 5, 5]

(notice how it stopped at the last term, 55, and also notice how the double digit values are broken up into separate elements.)

I have no problem breaking up the digits, its just the "calculating" that is giving me a hard time.. thanks in advance for any advice

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  • I almost understood... do you need an algorithm to generate the fibonacci sequence? Commented Feb 4, 2012 at 8:29
  • You just have to remember the two previous numbers to compute the next one. Use two variables in addition to your list. Commented Feb 4, 2012 at 8:29
  • breaking the digit does not make a sense. I guess what your teacher meant is, a list of String that looks like [1, 0+1, 1+1, 1+2, 3+2, 3+5, 5+8, ...] Commented Feb 4, 2012 at 8:31
  • Why did you clear your question??? Commented Feb 4, 2012 at 17:21

8 Answers 8

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2

I would generate Fibonacci values using int values and use these results to break up digits to add to the ArrayList.

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1

It sounds like you want to walk the Fibonacci sequence, starting with F1, while appending the digits as ints to an ArrayList<int> as you go. Since you want the digits in base-10, I think this would be easiest to read if you convert the intermediate Fibonacci integers to strings, then step through each char in the string as a character array. As you step through it, you can convert each digit back to an integer by subtracting the char '0' from it. You can then append the numerical version of that digit to the ArrayList<int>. The end result would look like something like this:

ArrayList<int> arrayList = new ArrayList<int>();

int a = 1;
int b = 0;
int n = 1;

while (n++ <= input) {  // input being from the user
    a += b;
    b = a - b;

    char[] fib = Integer.toString(b).toCharArray();
    for (int i = 0; i < fib.length; i++) {
        arrayList.add(fib[i] - '0');
    }
}

The takeaway here is that you don't mess around with your numerical values as you're walking up the Fibonacci sequence. Instead, you cache off a copy of 'b' that you transform into a string before determining the value of each digit that will go into the ArrayList<int>.

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1 Comment

You can always use long or BigInteger to get bigger values in a and b. As for the purpose of the exercise, are you saying you a can't store the intermediate Fibonacci values in local variables? Do you mean literally "everything" has to be stored in this ArrayList? It would help if you elaborated on your requirements here, since you obviously have to have some variable outside of the ArrayList to choose from before you put something into it.
1

Well When I tried to copy the Arraylist thing it came up with a syntax error, and the other response on this didn't have enough code to show what it actually would do. Either way though the assignment your teacher gave you is sorta of a waste of programming. Below is something that will give you the value for Fibonacci numbers. num is which Fibonacci number in the Fibonacci series you want. Example if you want the 6th fibonacci number in the series you would put fibi(6) for when you call it. 

public static int fibi(int num)
{
    int initial =0; int addtoinitial = 1;
    int keepinitial = 0;

    for(int i = 0; i <num; i++)
    {
        keepinitial = initial;
        initial = addtoinitial;
        addtoinitial = keepinitial + addtoinitial;
    }

    return initial;

}

A way you modify it so that you can get your string array, but right now I need to go to lunch

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1

Below is the way to make the string array. Reason for the and less than 46 is because that is how long the public array initialized length is, and you can't change the length outside of the initialization. You can just change what each piece in it is. Also in actually for int Fibonacci numbers for using their value if you try to use anything above the 46th fibonacci number it will go outside the max value for an int. If you use long its if you try to use something above the 92nd fibonacci number it will go outside the max value for a long.

public static void fibsmake(int num) {
    fibsreallength= num;
    int initial = 0; 
    int addtoinitial = 1;
    int keepinitial = 0;

    for(int i = 0; i<num&&i<46; i++) {
        keepinitial = initial;
        initial = addtoinitial;
        fibs[i]=keepinitial+"+"+initial;
        addtoinitial = keepinitial + addtoinitial;
    }
}


public static String fibs[]={"","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","","",""};
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2 Comments

{ int initial =0; int addtoinitial = 1; int keepinitial = 0; for(int i = 0; i<num&&i<46; i++) { keepinitial = initial; initial = addtoinitial; fibs[i]=keepinitial+"+"+initial; addtoinitial = keepinitial + addtoinitial; } }
above is what suppose to be in the method, but for some reason it won't post correctly for the answer section
1

i think this should workout.

package p1;

import java.util.ArrayList;

public class NEWtEST {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ArrayList a =new ArrayList();

        a.add(0);// enter the 1st elemnt of the list
        a.add(1);// 2nd elemnt
        int currIndex=1;
        while(currIndex<50)//--- i set the limit as first 50 items
        {
            a.add(((Integer)a.get(currIndex))+((Integer)a.get(currIndex-1)));
            currIndex++;
            System.out.print(a.get(currIndex)+ " ");
        }
    }

}
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Comments

0

  1. Write a classical (just, made nonrecursive, for Java) Fibonacci function.

  2. OK, you don't want fib(N), so change the test of your loop so that it continues until >=N is reached.

  3. Also, you don't want to return an int, but an ArrayList. So create one in your function, add to it in your loop, and return it.

  4. Oh, you also want to do that weird digit thing. Don't change your function from #3; instead, use it to get an ArrayList of Fibonacci numbers, and then iterate over that, adding digits to a new ArrayList.

Alternate #4, if Nishant is correct: loop from index 2 of the ArrayList returned by #3 and look backwards, as in

sums.add("1");
sums.add("0+1");
for (int i = 2; i < fibs.size(); i++)
  sums.add(fibs.get(i - 2).toString() + "+" + fibs.get(i - 1));

'course, in this case you could continue to edit your original Fibonacci function, and skip the production of the fibs ArrayList.

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0

I am not good at explaining. But i think this code can meet your requirement.

import java.util.*;

public class Fibonacci {

        public static void main(String[] args) {
                long temp1=0;
                long temp2=1;
                long temp3;
                int temp4;
                //number of elements to generate in a series
                Scanner sc = new Scanner(System.in);
                ArrayList<Integer> list = new ArrayList<Integer>();
                System.out.println("Enter Number ");
                int num = sc.nextInt(); 
                if(num==0)
                list.add(0);
                else if(num==1)
                list.add(1);
                else 
                {
                    list.add(0);
                    list.add(1);
                //create the Fibonacci series and store it in an arraylist
                for(int i=1; i < num; i++){
                    temp3= temp1+temp2;
                    temp1= temp2;
                    temp2=temp3;
                    do{
                        temp4=(int) temp3%10;
                        temp3= temp3/10;
                        list.add(temp4);
                    }while(temp3!=0);
                }
                }
                //print the Fibonacci series numbers

                System.out.println("Fibonacci Series upto " + num);
                System.out.print(list);

        }
}
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0 
    public static void main(String[] args) {
        List<Integer> numList = new ArrayList<>();

        Scanner sc = new Scanner(System.in);
        System.out.println("Please enter the size of the list:\n");
        int userInput = sc.nextInt();
        System.out.println("Your choose is"+" "+userInput);

        int a = 0;
        int b = 1;
        int c = 0;

        while(c<userInput) {
            c = a + b;
            a = b;
            b = c;

            numList.add(c);
        }

        System.out.println("Fibonacci list:"+" "+numList);
    }
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