How do you merge overlapping intervals using sorting?

Sort intervals by their start times. Initialize the result with the first interval. For each subsequent interval, compare its start with the end of the last interval in the result. If the start is less than or equal to the end of the last interval, they overlap: merge them by updating the end to the maximum of both ends. If the start is greater, there is no overlap: add the new interval to the result as a separate entry. This runs in O of n log n for sorting plus O of n for the merge pass.