Medium
Given an array of intervals (each [start, end]), merge all overlapping intervals and return the non-overlapping result sorted by start. On this judge intervals are shown separated by |.
Input: grid = [[1,3],[2,6],[8,10],[15,18]] Output: [[1,6],[8,10],[15,18]]
Input: grid = [[1,4],[4,5]] Output: [[1,5]]