This question evaluates skills in interval manipulation, schedule normalization, time parsing and time-zone handling, and scalable algorithm and data-structure selection for processing large sets of temporal intervals.
You are given schedules for multiple employees. schedules[i] is a list of busy intervals for employee i, where each interval is half-open [start, end) in minutes from 0 to 1440 for a single day. Return all maximal half-open intervals [s, e) during which every employee is free. Requirements: (