[백준] 11000 강의실 배정 - Greedy / Java

• 문제 링크

11000번: 강의실 배정

 

• 풀이 과정

 

• 풀이 코드

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
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));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        StringTokenizer st;

        int n = Integer.parseInt(br.readLine());

        List<Lecture> list = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            st = new StringTokenizer(br.readLine());
            int start = Integer.parseInt(st.nextToken());
            int end = Integer.parseInt(st.nextToken());

            list.add(new Lecture(start, end));
        }

        Collections.sort(list);

        PriorityQueue<Integer> pq = new PriorityQueue<>();
        pq.offer(list.get(0).end);

        for (int i = 1; i < n; i++) {
            if (pq.peek() <= list.get(i).start)
                pq.poll();

            pq.offer(list.get(i).end);
        }

        bw.write(String.valueOf(pq.size()));
        bw.flush();
    }

    private static class Lecture implements Comparable<Lecture> {
        int start, end;

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

        @Override
        public int compareTo(Lecture o) {
            return start == o.start ? end - o.end : start - o.start;
        }
    }

}