refer to: https://www.algoexpert.io/questions/Merge%20Overlapping%20Intervals
step 1: sort the intervals by their start value
step 2: check if the end value of the previous interval is larger than the start value of the latter interval
def mergeOverlappingIntervals(intervals): # sort the intervals by startinf value. O(nlogn) sortedIntervals = sorted(intervals, key = lambda x: x[0]) mergedIntervals = []# space: O(n) currentInterval = sortedIntervals[0]#initialize the currentInterval as the first interval of the intervals mergedIntervals.append(currentInterval)#initialize the mergedIntervals as the first interval of the intervals for nextInterval in sortedIntervals:# for the first iteration, no update _, currentIntervalEnd = currentInterval nextIntervalStart, nextIntervalEnd = nextInterval if currentIntervalEnd >= nextIntervalStart: # overlap found, update the end value of interval currentInterval[1] = max(currentIntervalEnd, nextIntervalEnd) else: # no overlap, add the current(nextInterval) into the mergedIntervals array currentInterval = nextInterval mergedIntervals.append(currentInterval) return mergedIntervals
O(nlogn) time complexity for sorting
O(n) space complexity for store the mergedIntervals(upper bound, all intervals kept)
原文：https://www.cnblogs.com/LilyLiya/p/15028663.html