Suppose you want to bring the whole company together for a gigantic meeting of the minds.
Your company has N employees, and you have their schedules available as N lists of <begin, end> timestamp pairs, which indicate times that each individual person is busy.
Each list is sorted and there are no overlaps within a single list.
Find a list of times (<begin, end> timestamp pairs) during which all N people are free.
You should specify a beginHour and endHour time. We don't care about times before or after that time
9 10 11 12 13 14 15 16 17 18 19
A |------|------|,,,,,,|------|,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,|
B |------|,,,,,,,,,,,,,|------|,,,,,,,,,,,,,|------|,,,,,,|------|,,,,,,|
Gide: (Free shows by ,,, and Busy shows by ---) The "Class Time{...}" has given in progect.