Merge pull request #495 from AlgorithmWithGod/03do-new30

[20250718] BOJ / G5 / 강의실 배정 / 신동윤

Author: ShinHeeEul

03do-new30/202507/18 BOJ G5 강의실 배정.md

@@ -0,0 +1,54 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main {
+    static int N;
+    static class Lecture {
+        int start;
+        int end;
+
+        public Lecture(int start, int end) {
+            this.start = start;
+            this.end = end;
+        }
+    }
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        N = Integer.parseInt(br.readLine());
+
+        Lecture[] lectures = new Lecture[N];
+
+        for (int i = 0; i < N; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            Lecture lecture =  new Lecture(Integer.parseInt(st.nextToken()), Integer.parseInt(st.nextToken()));
+            lectures[i] = lecture;
+        }
+
+        // 시작 시간 기준 오름차순 강의 정렬
+        Arrays.sort(lectures, new Comparator<Lecture>() {
+            @Override
+            public int compare(Lecture o1, Lecture o2) {
+                return Integer.compare(o1.start, o2.start);
+            }
+        });
+
+        // 끝나는 시간 기준 오름차순 우선순위 큐
+        PriorityQueue<Lecture> pq = new PriorityQueue<>(new Comparator<Lecture>() {
+            @Override
+            public int compare(Lecture o1, Lecture o2) {
+                return Integer.compare(o1.end, o2.end);
+            }
+        });
+
+        for (Lecture current : lectures) {
+            if (!pq.isEmpty() && pq.peek().end <= current.start) {
+                pq.poll(); // 기존 강의실
+            }
+            pq.offer(current);
+        }
+        System.out.println(pq.size());
+        br.close();
+    }
+}
+```