Intervals

Ranges with a start and end — sorting by start (or end) turns overlap and merge problems into a single linear pass.

Q1.Before merging overlapping intervals, what preprocessing step is almost always required?

Q2.Two intervals [a, b] and [c, d] (with a <= c) overlap if which condition holds?

Q3.What is the time complexity of merging n overlapping intervals after sorting?

Q4.For the "minimum number of meeting rooms needed" problem, what's a common efficient approach?