56.py

'''
	Given a collection of intervals, merge all overlapping intervals.

	Example 1:

	Input: [[1,3],[2,6],[8,10],[15,18]]
	Output: [[1,6],[8,10],[15,18]]
	Explanation: Since intervals [1,3] and [2,6] overlaps, merge them into [1,6].
	Example 2:

	Input: [[1,4],[4,5]]
	Output: [[1,5]]
	Explanation: Intervals [1,4] and [4,5] are considerred overlapping.
'''

# Definition for an interval.
# class Interval(object):
#     def __init__(self, s=0, e=0):
#         self.start = s
#         self.end = e

class compare(object):
	def __init__(self, interval):
		self.interval = interval

	def __lt__(self, other):
		if self.interval.start == other.interval.start:
			return self.interval.end < other.interval.end
		return self.interval.start < other.interval.end

class Solution(object):
    def merge(self, intervals):
        """
        :type intervals: List[Interval]
        :rtype: List[Interval]
        """
        
        intervals = sorted(intervals, key= compare)
        # intervals.sort(key=lambda x: x.start)
        merged = []
        for interval in intervals:
        	if not merged or merged[-1].end < interval.start:
        		merged.append(interval)
        	else:
        		merged[-1].end = max(merged[-1].end, interval.end)
        return merged

# Time: O(N*log(N))
# Space: O(1)