1288. Remove Covered Intervals

Problem Link

Description

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Given an array intervals where intervals[i] = [li, ri] represent the interval [li, ri), remove all intervals that are covered by another interval in the list.

The interval [a, b) is covered by the interval [c, d) if and only if c <= a and b <= d.

Return the number of remaining intervals.

 

Example 1:

Input: intervals = [[1,4],[3,6],[2,8]]
Output: 2
Explanation: Interval [3,6] is covered by [2,8], therefore it is removed.

Example 2:

Input: intervals = [[1,4],[2,3]]
Output: 1

 

Constraints:

• 1 <= intervals.length <= 1000
• intervals[i].length == 2
• 0 <= li < ri <= 105
• All the given intervals are unique.

Solution

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Python3

class Solution:
    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
        res = right = 0
        
        intervals.sort(key = lambda x:(x[0],-x[1]))
        
        for start,end in intervals:
            res += end > right
            right = max(right, end)
        
        return res