1288. Remove Covered Intervals

Problem

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 <= 10^5

• All the given intervals are unique.

Solution (Java)

class Solution {
    public int removeCoveredIntervals(int[][] intervals) {
        Queue<int[]> q = new PriorityQueue<>((a, b) -> a[0] == b[0] ? b[1] - a[1] : a[0] - b[0]);
        for (int[] interval : intervals) {
            q.offer(interval);
        }
        int[] prev = q.poll();
        int count = 0;
        while (!q.isEmpty()) {
            int[] curr = q.poll();
            if (curr[0] >= prev[0] && curr[1] <= prev[1]) {
                count++;
            } else {
                prev = curr;
            }
        }
        return intervals.length - count;
    }
}

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).