Problem

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.

Input

• A list of intervals, where each interval is represented as a list of two integers [start, end].

Output

• A list of merged intervals, where each interval is represented as a list of two integers.

Examples

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].

Constraints

• 1 <= intervals.length <= 10^4
• 0 <= intervals[i][0] <= intervals[i][1] <= 10^4.