Merge Intervals.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 Solution(object):
    def merge(self, intervals):
        """
        :type intervals: List[Interval]
        :rtype: List[Interval]
        """
        res = []
        if not intervals:
            return res
        intervals.sort(key = lambda x: (x.start, x.end))
        
        res.append(intervals[0])
        for i in xrange(1, len(intervals)):
            if intervals[i].start <= res[-1].end:
                res[-1].end = max(res[-1].end, intervals[i].end)
            else:
                res.append(intervals[i])
                
        return res