<p>Given an array <code>intervals</code> where <code>intervals[i] = [l<sub>i</sub>, r<sub>i</sub>]</code> represent the interval <code>[l<sub>i</sub>, r<sub>i</sub>)</code>, remove all intervals that are covered by another interval in the list.</p> <p>The interval <code>[a, b)</code> is covered by the interval <code>[c, d)</code> if and only if <code>c <= a</code> and <code>b <= d</code>.</p> <p>Return <em>the number of remaining intervals</em>.</p> <p> </p> <p><strong>Example 1:</strong></p> <pre> <strong>Input:</strong> intervals = [[1,4],[3,6],[2,8]] <strong>Output:</strong> 2 <strong>Explanation:</strong> Interval [3,6] is covered by [2,8], therefore it is removed. </pre> <p><strong>Example 2:</strong></p> <pre> <strong>Input:</strong> intervals = [[1,4],[2,3]] <strong>Output:</strong> 1 </pre> <p> </p> <p><strong>Constraints:</strong></p> <ul> <li><code>1 <= intervals.length <= 1000</code></li> <li><code>intervals[i].length == 2</code></li> <li><code>0 <= l<sub>i</sub> < r<sub>i</sub> <= 10<sup>5</sup></code></li> <li>All the given intervals are <strong>unique</strong>.</li> </ul>