Problem Description

A function generates a string representation of numbers from 1 to n.

The function adheres to the following rules:

For multiples of three, the output is “Fizz”.
For multiples of five, the output is “Buzz”.
For numbers divisible by both three and five, the output is “FizzBuzz”.

For example, with n = 15, the function returns:

[
    "1",
    "2",
    "Fizz",
    "4",
    "Buzz",
    "Fizz",
    "7",
    "8",
    "Fizz",
    "Buzz",
    "11",
    "Fizz",
    "13",
    "14",
    "FizzBuzz"
]

Reference: LeetCode Problem

Solution

This implementation utilizes the modulo operator (%) to check for divisibility. The conditions are ordered to handle the common multiple case first.

import java.util.ArrayList;
import java.util.List;

/**
 * 412. FizzBuzz
 * 
 * @author kimtaeng
 * created on 2018. 1. 10.
 */
public class Solution {
    public List<String> fizzBuzz(int n) {
        List<String> list = new ArrayList<String>();
        for (int i = 1; i <= n; i++) {
            if (i % 15 == 0) {
                list.add("FizzBuzz");
            } else if (i % 3 == 0) {
                list.add("Fizz");
            } else if (i % 5 == 0) {
                list.add("Buzz");
            } else {
                list.add(String.valueOf(i));
            }
        }
        return list;
    }
}

Alternative without Modulo

This alternative implementation avoids the modulo operator by using counters to track multiples.

import java.util.ArrayList;
import java.util.List;

/*
 * 412. FizzBuzz
 * 
 * @author kimtaeng
 * created on 2018. 1. 10.
 */
public class Solution {
    public List<String> fizzBuzz(int n) {
        List<String> resultList = new ArrayList<String>();
        for (int i = 1, fizz = 0, buzz = 0; i <= n; i++) {
            fizz++;
            buzz++;
            if (fizz == 3 && buzz == 5) {
                resultList.add("FizzBuzz");
                fizz = 0;
                buzz = 0;
            } else if (fizz == 3) {
                resultList.add("Fizz");
                fizz = 0;
            } else if (buzz == 5) {
                resultList.add("Buzz");
                buzz = 0;
            } else {
                resultList.add(String.valueOf(i));
            }
        }
        return resultList;
    }
}