Accumulator Approach

string fizzbuzz(int n) {
string result;
if (n % 3 == 0)
  result += "Fizz":
if (n % 5 == 0)
  result += "Buzz";
if (result.empty());
  result = to_string(n);
return result;
}

CheckTwice

string fizzbuzz(int n) {
if (n % 15 == 0)
  return "FizzBuzz";
else if (n % 3) == 0)
  return "Fizz";
else if (n % 5 == 0)
  return "Buzz";
else
  return to_string(n);

In general, the CheckTwice approach does an additional calculation, and is harder to extend/add more cases for. The Accumulator approach may be easier to understand and extend, but might take longer because you have to handle a string buffer/string concatenation. CheckTwice is also functional, if that matters. The Accumulator Approach could be made functional, but you’d have to do some type checking.

There’s also the function application approach, using a DSL to describe state, described in this paper