강의실 배정 - 11000번

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내 코드

package com.company;

import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = null;
        int N = Integer.parseInt(br.readLine());
        int[][] arr = new int[N][2];
        int answer = 0;
        int count = 0;


        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, ((o1, o2) -> o1[0] - o2[0]));
        PriorityQueue<Integer> pq = new PriorityQueue<>();

        for (int i = 0; i < N; i++) {
            while (!pq.isEmpty() && pq.peek() <= arr[i][0]) {
                pq.poll();
                count--;
            }

            if (pq.isEmpty() || pq.peek() > arr[i][0]) {
                count++;
                answer = Math.max(answer, count);
            }
            pq.add(arr[i][1]);
        }

        System.out.println(answer);
    }
}