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javaalgorithmlistrecursionfizzbuzz
alexjs000
alexjs000

Reputation: 85

Java FizzBuzz recursive solution

Attempting a FizzBuzz recursive solution in Java to return a list of Strings with n iterations. For example, n = 4 should output ["1","2","Fizz", 4]. However, with my current code the output is just ["4"]. Why is my solution not executing the recursive function? Any other critiques are appreciated!

class Solution {
public List<String> fizzBuzz(int n) {

    //create variable to return list of strings
    List<String> fbList = new ArrayList<String>();

    //base case 1
    if(n == 0){
        fbList.add(Integer.toString(0));
    }

    //base case 2
    else if(n == 1){
        fbList.add(Integer.toString(1));
    }    

    //OW take n and begin reducing recursively from, n - 1
    else{
        if(n % 3 == 0){
            fbList.add("Fizz");
        }
        else if(n % 5 == 0){
            fbList.add("Buzz");
        }
        else if((n % 3 == 0) && (n % 5 == 0)){
            fbList.add("FizzBuzz");
        }
        else{
            fbList.add(Integer.toString(n));
        }
        //recursive function call
        fizzBuzz(n - 1);
    }
    return fbList;
    }
}

Upvotes: 2

Views: 1522

Answers (2)

GBlodgett
GBlodgett

Reputation: 12819

The problem is that with every recursive call, a new List is created. You return the list but:

fizzBuzz(n - 1);

You are ignoring the return value of the recursive calls. To fix this you can do:

fbList.addAll(0, fizzBuzz(n - 1));

Which will utilize the method addAll to add all the elements returned by the recursive calls. This returns:

[1, 2, Fizz, 4]

However this is rather expensive for an ArrayList. You could change this to a LinkedList, which would allow for linear time adding.

Also you if/else if/else chain is out of order. if((n % 3 == 0) && (n % 5 == 0)) should be before if(n % 3 == 0) and if(n % 5 == 0). Otherwise it will always enter the if(n % 5 == 0) or if(n % 3 == 0):

if((n % 3 == 0) && (n % 5 == 0)){
    fbList.add("FizzBuzz");
}
else if(n % 3 == 0){
    fbList.add("Fizz");
}
else if(n % 5 == 0){
    fbList.add("Buzz");
}

Upvotes: 2

cdlane
cdlane

Reputation: 41872

Think simple when working with recursion, i.e. let recursion do the work. If your recursion is counting down but you want the list to come out ascending, add everything else first then add the thing you're working on:

import java.util.*;

public class Solution {

    public static List<String> pattern = Arrays.asList("FizzBuzz", "", "", "Fizz", "", "Buzz", "Fizz", "", "", "Fizz", "Buzz", "", "Fizz", "", "");

    public static List<String> fizzBuzz(int n) {

        List<String> fbList;

        if (n > 0) {
            fbList = fizzBuzz(n - 1);
            String string = pattern.get(n % pattern.size());
            fbList.add(string.isEmpty() ? Integer.toString(n) : string);
        } else {
            fbList = new ArrayList<String>();
        }

        return fbList;
    }

    public static void main(String[] args) {
        System.out.println(fizzBuzz(Integer.parseInt(args[0])));
    }
}

OUTPUT

> java Solution 35
[1, 2, Fizz, 4, Buzz, Fizz, 7, 8, Fizz, Buzz, 11, Fizz, 13, 14, FizzBuzz, 16, 17, Fizz, 19, Buzz, Fizz, 22, 23, Fizz, Buzz, 26, Fizz, 28, 29, FizzBuzz, 31, 32, Fizz, 34, Buzz]
>

Upvotes: 0

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