0056-merge-intervals

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Description

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] overlap, 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.

Example 3:

Input: intervals = [[4,7],[1,4]]
Output: [[1,7]]
Explanation: Intervals [1,4] and [4,7] are considered overlapping.

 

Constraints:

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

Solution(Python)

class Solution:
    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
        # intervals = [[1,3],[2,6],[8,10],[15,18]]
        # res = []
        #     = [1,3] i = 0
        # i = 1 ; 3 > 2  res = [1,6] 3 < 6
        # i =2 ;  6 > 8 false  res = [1,6], [8,10]
        # i =3    10 > 15 f   res = [1,6], [8,10] [15,18]
        intervals.sort(key=lambda x: x[0])
        res = [intervals[0]]
        for s,e in intervals[1:]:
            if s <= res[-1][1]:
                res[-1][1] = max(e,  res[-1][1])
            else:
                res.append([s,e])

        return res

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