Merge overlapping time intervals

## Problem: Merge Intervals You are given an array of intervals `intervals`, where each interval is a pair `[start, end]` with `start <= end`. Merge all overlapping intervals and return a new array of non-overlapping intervals that covers all the intervals in the input. ### Overlap definition Two intervals `[a,b]` and `[c,d]` overlap if `c <= b` (assuming `a <= c` after sorting). ### Input / Output - **Input:** `intervals: number[][]` - **Output:** `number[][]` merged intervals ### Example - Input: `[[1,3],[2,6],[8,10],[15,18]]` - Output: `[[1,6],[8,10],[15,18]]` ### Constraints - `1 <= intervals.length <= 10^5` - Interval values fit in 32-bit signed integers. ### Follow-ups - What is the time complexity of your approach? - How do you handle already-sorted vs unsorted inputs?