Parse strings and find meeting slots

Question

Given a text file where each line contains raw information, extract the user identifier and the numeric quantity on that line and store the results efficiently.

Given multiple people's calendars (each as a list of available days), return the days when everyone is available for a meeting. Follow-ups: (a) return the days when at least P people are available; (b) given an integer X, return time periods of consecutive days of length X when the availability condition holds.