Merge Intervals

Given a collection of intervals, merge all overlapping intervals. 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, they are merged into [1,6]. Example 2: Input: intervals = [[1,4],[4,5]] Output: [[1,5]] Explanation: Intervals [1,4] and [4,5] are considered overlapping. Constraints: intervals[i][0] <= intervals[i][1] Example Input [[1,3],[2,6],[8,10],[15,18]]