99클럽 코테 스터디 38일차 TIL + [LeetCode] 1845. Seat Reservation Manager/힙/JAVA풀이

 

 

 

 

 

 

1. 오늘의 학습 키워드

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[LeetCode] 1845. Seat Reservation Manager/힙/JAVA풀이

 

2. 오늘의 학습 문제 

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문제

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https://leetcode.com/problems/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.

 

코드

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import java.util.*;
 
class SeatManager {
 
    static PriorityQueue<Integer> pQ ;
    
    public SeatManager(int n) {
        
        pQ = new PriorityQueue<>(); //큐 초기화
        for(int i=0;i<n;i++)
            pQ.offer(i+1);
        
    }
    
    public int reserve() {
        return  pQ.poll();
    }
    
    public void unreserve(int seatNumber) {
        pQ.offer(seatNumber);
    }
}
 
/**
 * Your SeatManager object will be instantiated and called as such:
 * SeatManager obj = new SeatManager(n);
 * int param_1 = obj.reserve();
 * obj.unreserve(seatNumber);
 */

 

 

 

 

3. 오늘의 회고

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• 힙을 사용해 풀었다. 자동으로 내부적으로 정렬되어 편리한 자료구조같다.
• 2일남았다. 파이팅!