interval problems (ranges with start/end)s are ranges defined by start and end points. You process them by sorting and then scanning to detect overlaps, merge, or count. Sorting by start (or end) enables linear processing of interval relationships. Most interval problems reduce to: sort, then process pairs of adjacent intervals.
You'll see this in scheduling and range merging problems. If you can explain these concepts in your own words, you'll solve related problems faster under interview pressure.
