Intervals & Custom Sorting

Intervals come up more at Pinterest than the topic's reputation would suggest. A Premium question and its harder cousins land in phone screens. One onsite turned up a restaurant-seating capacity twist: find every window that can seat N guests given reservations and a room size. And the most-viewed Pinterest thread anyone has shared is a masonry-grid problem called "a Premium question." None of it is exotic. It is the same a Premium question, Insert Interval, Non-overlapping Intervals, My Calendar family you would drill for anywhere, in board-and-feed framing.

So treat this lesson as pattern reps, not as a Pinterest secret. The payoff is that two templates cover nearly every interval prompt you will see, and a third skill, writing a custom comparator and trusting it, quietly decides half of them. Get those three reflexes solid and the product framing stops mattering, because once you strip the Pin language off "a Premium question" you are looking at greedy interval scheduling and nothing more.

The Pinterest angle

When a prompt arrives framed as Pins, boards, or a scrolling feed, your first job is to find the interval underneath. A pin with a top and bottom pixel coordinate is an interval. A scroll session with an enter and exit position is an interval. A reservation with a start and end time is an interval. Say the translation out loud, "each pin is a span [top, bottom], and two pins collide when their spans overlap", before you write anything. It pins the problem down for the interviewer and stops you from inventing feed-specific machinery the question never needed.