# LeetCode 56. Merge Intervals

## Description

https://leetcode.com/problems/merge-intervals/

Given an array of `intervals` where `intervals[i] = [starti, endi]`, merge all overlapping intervals, and return an array of the non-overlapping intervals that cover all the intervals in the input.

Example 1:

```Input: intervals = [[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: intervals = [[1,4],[4,5]]
Output: [[1,5]]
Explanation: Intervals [1,4] and [4,5] are considered overlapping.
```

Constraints:

• `1 <= intervals.length <= 104`
• `intervals[i].length == 2`
• `0 <= starti <= endi <= 104`

## Explanation

First sorted the interval base on the start of elements. Then compare each interval start and end with the last merged interval to decide whether to merge.

## Python Solution

``````class Solution:
def merge(self, intervals: List[List[int]]) -> List[List[int]]:
result = []

intervals = sorted(intervals, key=lambda interval:interval[0])

for interval in intervals:
if len(result) == 0 or result[-1][1] < interval[0]:
result.append(interval)
else:
result[-1][1] = max(result[-1][1], interval[1])

return result``````
• Time complexity: ~ N
• Space complexity: ~1