Had screening round yesterday. Cant remember the exact question but it was someting along these lines.

You're building a streaming payment validator that receives a number as a digit-by-digit string. At every step, you need to check if the current prefix forms a number divisible by a given integer m.

Return an array div such that div[i] = 1 if the prefix from word[0..i] is divisible by m, else 0.
You cant store the numbers as they can be very large
Brute force is obvious but interviewer was not ammused, can anyone provide O(n) solution