Set

NavigableSet

Prefix	Suffix	Parameter	Comparison
ceiling		e	>=
floor		e	<=
higher		e	>
lower		e	<
head	set	toElement	<
head	set	toElement, inclusive	< or <=
tail	set	fromElement	>=
tail	set	fromElement, inclusive	> or >=
pollFirst			lowest
pollLast			highest
descending	iterator
descending	set
sub	set	fromElement, fromInclusive, toElement, toInclusive

SortedSet

Prefix	Suffix	Parameter	Comparison
head	set	toElement	<
tail	set	fromElement	>=
first			lowest
last			highest
sub	set	fromElement, toElement	[)

BitSet

Distribute Candies

private static final int MAX_NUM_TYPES = 2 * (int)1e5 + 1;

public int distributeCandies(int[] candyType) {
    BitSet bitset = new BitSet(MAX_NUM_TYPES);
    for (int c : candyType) {
        bitset.set(c + MAX_NUM_TYPES / 2);
    }
    return Math.min(candyType.length / 2, bitset.cardinality());
}

Closest Room

public int[] closestRoom(int[][] rooms, int[][] queries) {
    Arrays.sort(rooms, Comparator.comparingInt(r -> -r[1]));

    int k = queries.length;
    Integer[] qIndex = new Integer[k];
    for (int i = 0; i < k; i++) {
        qIndex[i] = i;
    }
    Arrays.sort(qIndex, Comparator.comparingInt(i -> -queries[i][1]));

    TreeSet<Integer> ids = new TreeSet<>();
    int j = 0;
    int[] answer = new int[k];
    for (int i : qIndex) {
        int preferred = queries[i][0], minSize = queries[i][1];

        while (j < rooms.length && rooms[j][1] >= minSize) {
            ids.add(rooms[j++][0]);
        }

        Integer f = ids.floor(preferred), c = ids.ceiling(preferred);
        answer[i] = -1;
        if (c != null) {
            answer[i] = c;
        }
        if (f != null && (answer[i] < 0 || Math.abs(f - preferred) <= Math.abs(answer[i] - preferred))) {
            answer[i] = f;
        }
    }
    return answer;
}