You are given an integer n. Your task:

Return a list of strings from 1 to n following these rules:

1. If the number is divisible by 3 → output "Fizz"
2. If divisible by 5 → output "Buzz"
3. If divisible by both 3 and 5 → output "FizzBuzz"
4. Otherwise → output the number itself as a string

Example:

Input: n = 5
Output: ["1","2","Fizz","4","Buzz"]

Another example:

Input: n = 15
Output: ["1","2","Fizz","4","Buzz","Fizz","7","8","Fizz","Buzz",
         "11","Fizz","13","14","FizzBuzz"]

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Problem Understanding

Important details:

• Output type is a list of strings, not integers
• Order must be from 1 to n
• Multiples of both 3 and 5 must output "FizzBuzz" — this condition must be checked first
• No extra formatting or spacing
• n can be as large as 10⁴, so a simple loop is sufficient

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Logic Explained in Simple English

Here’s the simplest way to think about it:

1. Loop from 1 up to n
2. For each number:
   • First check if it’s divisible by 3 and 5
     • If yes, add "FizzBuzz"
   • Else if divisible by 3
     • Add "Fizz"
   • Else if divisible by 5
     • Add "Buzz"
   • Else
     • Convert number to string and add it

Why check 3 and 5 first?

Because if we check 3 first, then multiples like 15 would be labeled "Fizz" before "FizzBuzz", producing the wrong output.

This ensures correct priority and correctness.

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Step-by-Step Approach

1. Create an empty list of strings
2. Loop i from 1 to n
3. For each i:
   • If i % 15 == 0 → add “FizzBuzz”
   • Else if i % 3 == 0 → add “Fizz”
   • Else if i % 5 == 0 → add “Buzz”
   • Else → add String.valueOf(i)
4. Return the list

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Java Implementation

class Solution {
    public List<String> fizzBuzz(int n) {
        List<String> result = new ArrayList<>();
        
        for (int i = 1; i <= n; i++) {
            if (i % 15 == 0) {
                result.add("FizzBuzz");
            } else if (i % 3 == 0) {
                result.add("Fizz");
            } else if (i % 5 == 0) {
                result.add("Buzz");
            } else {
                result.add(String.valueOf(i));
            }
        }
        
        return result;
    }
}

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Dry Run Example

Input:

n = 10

Loop and output:

1 → “1” (not divisible by 3 or 5)
2 → “2”
3 → “Fizz”
4 → “4”
5 → “Buzz”
6 → “Fizz”
7 → “7”
8 → “8”
9 → “Fizz”
10 → “Buzz”

Final output:

["1","2","Fizz","4","Buzz","Fizz","7","8","Fizz","Buzz"]

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Time and Space Complexity

Time Complexity

O(n)

One loop through numbers 1 to n

Space Complexity

O(n)

Result list stores n strings

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Common Mistakes and How to Avoid Them

Mistake 1: Checking divisible by 3 before checking divisible by both

This incorrectly labels 15 as "Fizz"

Mistake 2: Returning integers instead of strings

Every entry must be a string

Mistake 3: Using concatenation logic incorrectly

This problem has fixed category outputs, not combinations like "FizzBuzzFizz"

Mistake 4: Off-by-one in loop bounds

Must loop from 1 through n inclusive

Mistake 5: Using slow string operations unnecessarily

Simple string literals are enough