Schrödinger Fullstack Engineer interview questions

Applied in October and received email three months later to schedule an interview. They scheduled an interview way earlier than I had wanted to and when I entered Google Hangouts for the interview I had trouble hearing the interviewer and now I had to reschedule the interview to today. It was a very positive experience. One round of Hangouts interview on a google doc. Coding question was Given a string containing '(', ')', '{', '}', '[' and ']', determine if the string is correctly balanced.