原题地址：https://leetcode.com/problems/merge-intervals/

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 considered overlapping.

**NOTE:** input types have been changed on April 15, 2019. Please reset to default code definition to get new method signature.