[백준] 11000번 : 강의실 배정[Java]

#풀이

import java.io.*;
import java.util.Arrays;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) throws IOException {
       BufferedReader br =  new BufferedReader(new InputStreamReader(System.in));
       int N = Integer.parseInt(br.readLine());
       int[][] arr = new int[N][2];
       StringTokenizer st;
       for(int i = 0; i<N; i++){
           st = new StringTokenizer(br.readLine());
           arr[i][0] = Integer.parseInt(st.nextToken());
           arr[i][1] = Integer.parseInt(st.nextToken());
       }
       Arrays.sort(arr,(a,b)->Integer.compare(a[0],b[0]));
        PriorityQueue<Integer> q = new PriorityQueue<>();
        q.add(arr[0][1]);
        for(int i = 1; i<arr.length; i++){
            if(arr[i][0]>=q.peek()){
                q.poll();
                q.add(arr[i][1]);
            }
            else q.add(arr[i][1]);
        }
        System.out.println(q.size());

    }
}

#성능

#정리

시작 시간 기준으로 수업을 정렬한 뒤, 우선순위 큐로 현재 진행 중인 수업들의 종료 시간을 관리한다.
새 수업이 가장 빨리 끝나는 수업 이후에 시작되면 강의실을 재사용하고, 그렇지 않으면 새 강의실을 배정한다.
큐의 크기가 사용하는 강의실의 개수이다.