Your question is First Non-Repeating Character. Start with the requirements on the right.
Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.
Given a string s, return the index of the first character that appears exactly once. If no such character exists, return -1.
1 <= len(s) <= 10^5s contains lowercase English letters-1 if there is no answer