！！！注意判空

！！！注意给定区间是否有序

# class Interval:
#     def __init__(self, a=0, b=0):
#         self.start = a
#         self.end = b

#
# 
# @param intervals Interval类一维数组 
# @return Interval类一维数组
#
class Solution:
    def merge(self , intervals ):
        # write code here
        if not intervals:
            return []

        intervals = sorted(intervals, key = lambda interval: interval.start)

        curr = intervals[0]

        res = []

        for i in range(1, len(intervals)):
            if curr.start <= intervals[i].start <= curr.end:
                curr.end = max(curr.end, intervals[i].end)
            else:
                res.append(curr)
                curr = intervals[i]

        res.append(curr)

        return res