baekjoon 1931 : 회의실 배정 https://www.acmicpc.net/problem/1931

baekjoon1931.java

import java.io.FileInputStream;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

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

public class Main {
	public static void main(String[] args) {
	Scanner sc = new Scanner(System.in);
	int length = sc.nextInt();
	Meeting[] meeting = new Meeting[length];
	for (int i = 0; i < length; i++) {
 		meeting[i] = new Meeting(sc.nextInt(), sc.nextInt());
	}
	Arrays.sort(meeting, new Comparator<Meeting> (){ //뒤가 짧아야 더 많이 배정할 수 있다고 가정.
	@Override 
	public int compare(Meeting a, Meeting b) {
		if (a.end == b.end) { //뒤가 같으면
			return Integer.compare(a.start, b.start); //앞에 것 비교
		} //뒤가 같지 않으면
		return Integer.compare(a.end, b.end); //뒤 비교
		}
	});

	int pick = 0;
	int ctn = 0;
	for (int i = 0; i < length; i++) {
  		if (pick <= meeting[i].start) {
   			pick = meeting[i].end;
			ctn++;
		}
	}

	System.out.println(ctn);
	}
}