Merge Intervals

The canonical LeetCode 56 prompt: merge every overlapping interval and return the non-overlapping intervals that cover the same ranges. Requirements Given an array of intervals where each interval is [start, end], merge all overlapping intervals. Return the resulting non-overlapping intervals covering the same ranges. Preserve closed-interval overlap semantics: intervals that touch at an endpoint merge. Examples Input: intervals = [[1,3],[2,6],[8,10],[15,18]] Output: [[1,6],[8,10],[15,18]] Input: intervals = [[1,4],[4,5]] Output: [[1,5]] Notes The prompt was identified as LC 56 without an additional twist. The screen began with a resume discussion and technical-challenge follow-ups, followed by roughly 25 minutes for coding. A newer screen used this as the first of two coding tasks. Finishing it quickly led directly to a transactional database-update exercise, so budget time for a possible second prompt even when the first task is familiar. Preparation Implement the sort-and-scan solution from a blank editor and explain the overlap invariant before writing code. Drill touching endpoints, nested intervals, a single interval, and input presented in reverse order. State the time and space costs, including whether the output array is counted as auxiliary space.