Given a list of intervals, remove all intervals that are covered by another interval in the list.
Interval [a,b) is covered by interval [c,d) if and only if c <= a and b <= d.
After doing so, 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
Example 3:
Input: intervals = [[0,10],[5,12]]
Output: 2
Example 4:
Input: intervals = [[3,10],[4,10],[5,11]]
Output: 2
Example 5:
Input: intervals = [[1,2],[1,4],[3,4]]
Output: 1
Constraints:
1 <= intervals.length <= 1000
intervals[i].length == 2
0 <= intervals[i][0] < intervals[i][1] <= 10^5
All the intervals are unique.
class Solution:
    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
        exclusion_set = set()
        for i in range(len(intervals)):
            for j in range(i+1,len(intervals)):
                a,b = intervals[i]
                c,d = intervals[j]
                if c <= a and b <= d:
                    exclusion_set.add((a,b))
                if a <= c and d <= b:
                    exclusion_set.add((c,d))
        return len(intervals) - len(exclusion_set)                   
class Solution:
    def removeCoveredIntervals(self, intervals: List[List[int]]) -> int:
        exclusion_set = set()
        for i in range(len(intervals)):
            for j in range(i+1,len(intervals)):
                a,b = intervals[i]
                c,d = intervals[j]
                if c <= a and b <= d:
                    exclusion_set.add((a,b))
                if a <= c and d <= b:
                    exclusion_set.add((c,d))
        return len(intervals) - len(exclusion_set)                   