[Greedy] 백준 - 강의실배정

-자바

package greedy;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

class Lecture {
	int start;
	int end;
	
	Lecture(int start, int end) {
		this.start = start;
		this.end = end;
	}
}

public class classroom_1 {
	public static void main(String[] args) throws NumberFormatException, IOException {
		BufferedReader br = new BufferedReader( new InputStreamReader(System.in));
		BufferedWriter bw = new BufferedWriter( new OutputStreamWriter(System.out));
		StringTokenizer st;
		
		int N = Integer.parseInt( br.readLine() );
		Lecture[] lectures = new Lecture[N];
		for( int i=0; i<N; i++ ) {
			st = new StringTokenizer(br.readLine());
			
			int start = Integer.parseInt(st.nextToken());
			int end = Integer.parseInt(st.nextToken());
			lectures[i] = new Lecture(start, end);
		}
		
		Arrays.sort(lectures, (l1, l2) -> l1.start == l2.start ? l1.end - l2.end : l1.start - l2.start);
		
		PriorityQueue<Integer> pq = new PriorityQueue<>();
		pq.offer( lectures[0].end );
		
		for( int i=1; i<N; i++ ) {
			if( pq.peek() <= lectures[i].start ) {
				pq.poll();
			}
			pq.offer(lectures[i].end);
		}
		
		bw.write( pq.size() + "\n" );
		bw.flush();
		bw.close();
		br.close();
		

	}
}