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How do I write FizzBuzz well?

Interview Prep 2 min read
Short answer

Check the combined condition first, or build the string by appending. Both avoid the repeated i % 15 check and both extend cleanly.

python
for i in range(1, 101):
    if i % 15 == 0:
        print("FizzBuzz")
    elif i % 3 == 0:
        print("Fizz")
    elif i % 5 == 0:
        print("Buzz")
    else:
        print(i)

Correct, and fine as a first answer. Order matters: put the 15 case first or it is never reached.

#The version that extends

python
for i in range(1, 101):
    output = ""
    if i % 3 == 0: output += "Fizz"
    if i % 5 == 0: output += "Buzz"
    print(output or i)

No % 15 at all — it falls out of both conditions being true. Adding a seventh rule means one more if, not four more branches.

output or i uses the fact that an empty string is falsy.

#Fully data-driven

python
RULES = [(3, "Fizz"), (5, "Buzz"), (7, "Bang")]

for i in range(1, 101):
    output = "".join(word for n, word in RULES if i % n == 0)
    print(output or i)

Now the rules are data. Whether this is better depends entirely on whether the rules actually change — offering it and saying that is the right move.

#What the interviewer is watching for

  • Do you handle the 15 case, or print "Fizz" for 15?
  • Do you start at 1 or 0?
  • Do you talk before typing?
  • If asked to add a rule, does your solution absorb it or need restructuring?

#Do not over-engineer it

Presenting a class hierarchy with a strategy pattern for FizzBuzz reads as poor judgement, not sophistication. Write the clear version, mention how you would extend it, and move on.

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