1288. Remove Covered Intervals

Medium

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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.

class Solution:
    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
        intervals.sort(key=lambda x : (x[0], x[0] - x[1]))
        # print(intervals)
        index = 0
        removing_index = []
        while index < len(intervals):
            x,y = intervals[index]
            while index+1 < len(intervals) and x <= intervals[index+1][0] and y >= intervals[index+1][1]:
                removing_index.append(index+1)
                index += 1
            index += 1
        # print(removing_index)
        return len(intervals) - len(removing_index)