Remove Covered Intervals

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:

import bisect

class Solution:
    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
        intervals.sort(key = lambda p: (p[0], p[0] - p[1]))
        n = len(intervals)
        i = 0
        while i < len(intervals):
            a, b = intervals[i]
            j = i + 1
            while j < len(intervals) and intervals[j][0] <= b:
                c, d = intervals[j]
                if d <= b:
                    intervals.pop(j)
                else:
                    j += 1
            i += 1
        return len(intervals)