#840 · #1288 · Remove Covered Intervals(删除被覆盖区间)

You are given an array of intervals intervals. Remove all intervals that are covered by another interval (an interval [a, b] is covered by [c, d] if c <= a and b <= d). Return the number of remaining intervals. Constraints: 1 <= intervals.length <= 1000, 0 <= intervals[i][0] <= intervals[i][1] <= 10^5, all intervals are distinct.