[20251023] BOJ / G3 / 나는 가르친다 스위핑을 / 한종욱

Author: Ukj0ng

Ukj0ng/202510/23 BOJ G3 나는 가르친다 스위핑을.md

@@ -0,0 +1,83 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static List<Event> events;
+    private static int N;
+    public static void main(String[] args) throws IOException {
+        init();
+        int answer = sweep();
+
+        bw.write(answer + "\n");
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        N = Integer.parseInt(br.readLine());
+
+        events = new ArrayList<>();
+
+        for (int i = 1; i <= N; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int x1 = Integer.parseInt(st.nextToken());
+            int y1 = Integer.parseInt(st.nextToken());
+            int x2 = Integer.parseInt(st.nextToken());
+            int y2 = Integer.parseInt(st.nextToken());
+
+            double angle1 = Math.atan2(y1, x1);
+            double angle2 = Math.atan2(y2, x2);
+
+            if (angle1 > angle2) {
+                double temp = angle1;
+                angle1 = angle2;
+                angle2 = temp;
+            }
+
+            events.add(new Event(angle1, i, true));
+            events.add(new Event(angle2, i, false));
+        }
+
+        events.sort((o1, o2) -> {
+            if (o1.angle == o2.angle) {
+                if (o1.start != o2.start) return o1.start ? -1 : 1;
+                return 0;
+            }
+
+            return Double.compare(o1.angle, o2.angle);
+        });
+    }
+
+    private static int sweep() {
+        int result = 0;
+        int count = 0;
+
+        for (Event event : events) {
+            if (event.start) {
+                count++;
+                result = Math.max(result, count);
+            } else {
+                count--;
+            }
+        }
+
+        return result;
+    }
+
+    static class Event {
+        double angle;
+        int index;
+        boolean start;
+
+        public Event(double angle, int index, boolean start) {
+            this.angle = angle;
+            this.index = index;
+            this.start = start;
+        }
+    }
+}
+```