Closest Room
<p>There is a hotel with <code>n</code> rooms. The rooms are represented by a 2D integer array <code>rooms</code> where <code>rooms[i] = [roomId<sub>i</sub>, size<sub>i</sub>]</code> denotes that there is a room with room number <code>roomId<sub>i</sub></code> and size equal to <code>size<sub>i</sub></code>. Each <code>roomId<sub>i</sub></code> is guaranteed to be <strong>unique</strong>.</p>

<p>You are also given <code>k</code> queries in a 2D array <code>queries</code> where <code>queries[j] = [preferred<sub>j</sub>, minSize<sub>j</sub>]</code>. The answer to the <code>j<sup>th</sup></code> query is the room number <code>id</code> of a room such that:</p>

<ul>
	<li>The room has a size of <strong>at least</strong> <code>minSize<sub>j</sub></code>, and</li>
	<li><code>abs(id - preferred<sub>j</sub>)</code> is <strong>minimized</strong>, where <code>abs(x)</code> is the absolute value of <code>x</code>.</li>
</ul>

<p>If there is a <strong>tie</strong> in the absolute difference, then use the room with the <strong>smallest</strong> such <code>id</code>. If there is <strong>no such room</strong>, the answer is <code>-1</code>.</p>

<p>Return <em>an array </em><code>answer</code><em> of length </em><code>k</code><em> where </em><code>answer[j]</code><em> contains the answer to the </em><code>j<sup>th</sup></code><em> query</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> rooms = [[2,2],[1,2],[3,2]], queries = [[3,1],[3,3],[5,2]]
<strong>Output:</strong> [3,-1,3]
<strong>Explanation: </strong>The answers to the queries are as follows:
Query = [3,1]: Room number 3 is the closest as abs(3 - 3) = 0, and its size of 2 is at least 1. The answer is 3.
Query = [3,3]: There are no rooms with a size of at least 3, so the answer is -1.
Query = [5,2]: Room number 3 is the closest as abs(3 - 5) = 2, and its size of 2 is at least 2. The answer is 3.</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> rooms = [[1,4],[2,3],[3,5],[4,1],[5,2]], queries = [[2,3],[2,4],[2,5]]
<strong>Output:</strong> [2,1,3]
<strong>Explanation: </strong>The answers to the queries are as follows:
Query = [2,3]: Room number 2 is the closest as abs(2 - 2) = 0, and its size of 3 is at least 3. The answer is 2.
Query = [2,4]: Room numbers 1 and 3 both have sizes of at least 4. The answer is 1 since it is smaller.
Query = [2,5]: Room number 3 is the only room with a size of at least 5. The answer is 3.</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>n == rooms.length</code></li>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>k == queries.length</code></li>
	<li><code>1 &lt;= k &lt;= 10<sup>4</sup></code></li>
	<li><code>1 &lt;= roomId<sub>i</sub>, preferred<sub>j</sub> &lt;= 10<sup>7</sup></code></li>
	<li><code>1 &lt;= size<sub>i</sub>, minSize<sub>j</sub> &lt;= 10<sup>7</sup></code></li>
</ul>
Array; Binary Search; Ordered Set; Sorting
func closestRoom(rooms [][]int, queries [][]int) []int {
	n, k := len(rooms), len(queries)
	sort.Slice(rooms, func(i, j int) bool { return rooms[i][1] < rooms[j][1] })
	idx := make([]int, k)
	ans := make([]int, k)
	for i := range idx {
		idx[i] = i
		ans[i] = -1
	}
	sort.Slice(idx, func(i, j int) bool { return queries[idx[i]][1] < queries[idx[j]][1] })
	rbt := redblacktree.NewWithIntComparator()
	merge := func(rbt *redblacktree.Tree, key, value int) {
		if v, ok := rbt.Get(key); ok {
			nxt := v.(int) + value
			if nxt == 0 {
				rbt.Remove(key)
			} else {
				rbt.Put(key, nxt)
			}
		} else {
			rbt.Put(key, value)
		}
	}
	for _, room := range rooms {
		merge(rbt, room[0], 1)
	}
	i := 0

	for _, j := range idx {
		prefer, minSize := queries[j][0], queries[j][1]
		for i < n && rooms[i][1] < minSize {
			merge(rbt, rooms[i][0], -1)
			i++
		}
		if i == n {
			break
		}
		c, _ := rbt.Ceiling(prefer)
		f, _ := rbt.Floor(prefer)
		if c != nil {
			ans[j] = c.Key.(int)
		}
		if f != nil && (ans[j] == -1 || ans[j]-prefer >= prefer-f.Key.(int)) {
			ans[j] = f.Key.(int)
		}
	}
	return ans
}