# Question

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.
```

# Intuition

If we sort the intervals by their start value, then each set of intervals that can be merged will appear as a contiguous “run” in the sorted list.

# Solution

```
# Definition for an interval.
# class Interval:
# def __init__(self, s=0, e=0):
# self.start = s
# self.end = e
class Solution:
def merge(self, intervals):
"""
:type intervals: List[Interval]
:rtype: List[Interval]
"""
if len(intervals) <= 1:
return intervals
intervals.sort(key=lambda x: x.start)
res = list()
current = intervals[0]
for intv in intervals[1:]:
if intv.start > current.end:
res.append(current)
current = intv
else:
current.end = intv.end if intv.end > current.end else current.end
res.append(current)
return res
```