function isDivisibleByThree(num: string): boolean {
      let mod3 = "012012012012";
      let modulo = "0";
      for (const digit of num) {
          modulo = mod3[Number(digit) + Number(modulo)];
      }
      return modulo === "0";
  }

"The programmer can use whatever representation they see fit with the only restriction being that it could only contain letters, numbers and symbols that could be typed with a single stroke"

All math operations can be implemented with bitwise operators, too, i am pretty sure

Likely the interviewer specifically needed the candidate to do that, implement the math, and tried to steer them that way numerous times (no sum table, dont use the type system, no math operators). Thats likely also why they suggest allowing limited use of Google, because they realize many people will need a refresher on bitwise operations. But they don’t want to outright tell you what to search for, they needed to see some resourcefulness. When they suggested OP was cheating they likely didn’t mean it personally and actually wanted to help steer OP towards an acceptable solution. Rather than saying it’s cheating they could have said it avoids the main thing we need to see, or outright say “please implement the low level math from first principles”

In my opinion the candidate showed resourcefulness in their own way indeed, but sometimes its not even up to the person administering an interview for example if they have been given a rubric.