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.
- A 2D array representing intervals.
- A 2D array representing merged intervals.
- 1 <= intervals.length <= 10^4
- intervals[i].length == 2
- 0 <= start_i <= end_i <= 10^4
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 are merged into [1, 6].