Given a collection of intervals, merge all overlapping intervals and return an array of the non-overlapping intervals that cover all the intervals in the input.
[start, end].Example 1:
Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Intervals [1,3] and [2,6] overlap, merge them to [1,6].
Example 2:
Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] touch but do not overlap, merge them to [1,5].
1 <= intervals.length <= 10^40 <= intervals[i][0] <= intervals[i][1] <= 10^4.