Given an array of intervals where intervals[i] = [start_i, end_i], merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.
Example 1:
Input: intervals = [[1,3],[2,6],[8,10],[15,18]]
Output: [[1,6],[8,10],[15,18]]
Explanation: Since intervals [1,3] and [2,6] overlap, merge them into [1,6].
Example 2:
Input: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping because they share endpoint 4.
Example 3:
Input: intervals = [[1,4],[0,4]]
Output: [[0,4]]
Explanation: After sorting by start, [0,4] comes first and fully contains [1,4].
1 <= intervals.length <= 10^4intervals[i].length == 20 <= start_i <= end_i <= 10^4