Usage of Inbuilt Functions In Coding Interview's

At a high level, candidates are allowed to use as many built-in functions as they like, as long as it doesn’t make the solution trivial.

Example: Multiply two large numbers A and B. 1 <= A, B <= 10^300

Intent: The interviewer wants to see how the number will be stored in memory (array vs. list), how operations like carry-over will be performed, etc…

Solution 1:

A language like Java has in-built libraries that make coding the solution trivial.

BigInteger x = new BigInteger(“1234…”); 
BigInteger y = new BigInteger(“9876…”); 
BigInteger result = x.multiply(y);

These libraries will not be allowed.

Solution 2:

On the other hand, you may use in-built libraries to store the number. Like an ArrayList.

List<Integer> digits = new ArrayList<>(); 
while(number > 0){ 
    digits.add(number % 10); 
    number = number / 10; 
}

Despite using an ArrayList over building a custom list (with node and tail pointer), this is allowed. Because the requirement of testing the candidate’s logic, coding, and communication skills are met.

Lastly, third-party libraries are a strict no for most interviews. It’s best to clarify with the interviewer when in doubt.

All the best!