Write merge_intervals(intervals) merging overlapping [start, end] intervals, returned sorted by start.
merge_intervals([[1, 3], [2, 6], [8, 10], [15, 18]]) → [[1, 6], [8, 10], [15, 18]]
merge_intervals([]) → []
Submit runs 4 tests, including hidden edge cases.
Run your code to see the output here.