Merge Intervals

Given an array of intervals where intervals[i] = [start, end], merge every pair that overlaps and return the intervals that remain.

Intervals that touch at a point (e.g. [1, 4] and [4, 5]) count as overlapping.

You may return the output in any order.

Example 1:

Input:  intervals = [[1,3], [2,6], [8,10], [15,18]]
Output: [[1,6], [8,10], [15,18]]
Explanation: [1,3] and [2,6] overlap, so they become [1,6].

Example 2:

Input:  intervals = [[1,4], [4,5]]
Output: [[1,5]]
Explanation: they meet at 4, which counts as overlapping.

Constraints:

• 1 <= len(intervals) <= 10^4
• intervals[i].length == 2
• 0 <= start <= end <= 10^4