1845. Seat Reservation Manager
Design a system that manages the reservation state of n seats that are numbered from 1 to n.
Implement the SeatManager class:
- SeatManager(int n) Initializes a SeatManager object that will manage n seats numbered from 1 to n. All seats are initially available.
- int reserve() Fetches the smallest-numbered unreserved seat, reserves it, and returns its number.
- void unreserve(int seatNumber) Unreserves the seat with the given seatNumber.
Example 1:
Input
["SeatManager", "reserve", "reserve", "unreserve", "reserve", "reserve", "reserve", "reserve", "unreserve"]
[[5], [], [], [2], [], [], [], [], [5]]
Output
[null, 1, 2, null, 2, 3, 4, 5, null]
Explanation SeatManager seatManager = new SeatManager(5); // Initializes a SeatManager with 5 seats. seatManager.reserve(); // All seats are available, so return the lowest numbered seat, which is 1. seatManager.reserve(); // The available seats are [2,3,4,5], so return the lowest of them, which is 2. seatManager.unreserve(2); // Unreserve seat 2, so now the available seats are [2,3,4,5]. seatManager.reserve(); // The available seats are [2,3,4,5], so return the lowest of them, which is 2. seatManager.reserve(); // The available seats are [3,4,5], so return the lowest of them, which is 3. seatManager.reserve(); // The available seats are [4,5], so return the lowest of them, which is 4. seatManager.reserve(); // The only available seat is seat 5, so return 5. seatManager.unreserve(5); // Unreserve seat 5, so now the available seats are [5].
Constraints:
- 1 <= n <= 105
- 1 <= seatNumber <= n
- For each call to reserve, it is guaranteed that there will be at least one unreserved seat.
- For each call to unreserve, it is guaranteed that seatNumber will be reserved.
- At most 105 calls in total will be made to reserve and unreserve.
Solution
cclass SeatManager {
BitSet bits;
public SeatManager(int n) {
bits = new BitSet(n);
}
public int reserve() {
int pos = bits.nextClearBit(1);
bits.set(pos);
return pos;
}
public void unreserve(int seatNumber) {
bits.flip(seatNumber);
}
}
class SeatManager1 {
PriorityQueue<Integer> pq = new PriorityQueue<>();
int curr = 1;
public SeatManager1(int n) {
// for (int i = 1; i <= n; i++) {
// pq.add(i);
// }
}
public int reserve() {
if (pq.size() > 0) {
return pq.poll();
}
return curr++;
}
public void unreserve(int seatNumber) {
pq.add(seatNumber);
}
}
class SeatManager2 {
PriorityQueue<Integer> pq = new PriorityQueue<>();
public SeatManager2(int n) {
for (int i = 1; i <= n; i++) {
pq.add(i);
}
}
public int reserve() {
return pq.poll();
}
public void unreserve(int seatNumber) {
pq.add(seatNumber);
}
}
/**
[null, 1, 2, null, 2, 3, 4, 5, null]
[null,1,2,null,2,3,4,5,null]
* Your SeatManager object will be instantiated and called as such:
* SeatManager obj = new SeatManager(n);
* int param_1 = obj.reserve();
* obj.unreserve(seatNumber);
*/