[20250211] BOJ / 플래5 / 선분 그룹 / 권혁준

khj20006/202502/11 BOJ P5 선분 그룹.md

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+```java
+
+import java.util.*;
+import java.io.*;
+
+class Point{
+	int x, y;
+	Point(int x, int y){
+		this.x = x;
+		this.y = y;
+	}
+
+	public int ccw(Point a, Point b) {
+		int x1 = this.x, y1 = this.y;
+		int x2 = a.x, y2 = a.y;
+		int x3 = b.x, y3 = b.y;
+		int res = (x1*y2 + x2*y3 + x3*y1) - (x1*y3 + x2*y1 + x3*y2); 
+		return res > 0 ? 1 : (res < 0 ? -1 : 0);
+	}
+
+}
+
+class Line{
+	Point a, b;
+	Line(int x1, int y1, int x2, int y2){
+		if(x1 < x2 || (x1 == x2 && y1 < y2)) {
+			a = new Point(x1,y1);
+			b = new Point(x2,y2);			
+		}
+		else {
+			a = new Point(x2,y2);
+			b = new Point(x1,y1);
+		}
+	}
+
+	public boolean intersect(Line o) {
+		int cond1 = this.a.ccw(this.b, o.a);
+		int cond2 = this.b.ccw(this.a, o.b);
+		int cond3 = o.a.ccw(o.b, this.a);
+		int cond4 = o.b.ccw(o.a, this.b);
+
+
+		if(cond1*cond2 < 0 || cond3*cond4 < 0) return false;
+		if(cond1*cond2 > 0 && cond3*cond4 > 0) return true;
+		if(cond1 == 0) {
+			if(this.between(o.a)) return true; 
+		}
+		if(cond2 == 0) {
+			if(this.between(o.b)) return true; 
+		}
+		if(cond3 == 0) {
+			if(o.between(this.a)) return true;
+		}
+		if(cond4 == 0) {
+			if(o.between(this.b)) return true;
+		}
+		return false;
+
+	}
+
+	public boolean between(Point p) {
+		return this.a.x<=p.x&&p.x<=this.b.x && (this.a.y<=p.y&&p.y<=this.b.y || this.b.y<=p.y&&p.y<=this.a.y);
+	}
+
+}
+
+class Main {
+
+	// IO field
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	static StringTokenizer st;
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	static long nextLong() {return Long.parseLong(st.nextToken());}
+	static void bwEnd() throws Exception {bw.flush();bw.close();}
+
+	// Additional field
+	static Line[] arr;
+	static int N;
+	static int[] root, cnt;
+
+	public static void main(String[] args) throws Exception {
+
+		ready();
+		solve();
+
+		bwEnd();
+	}
+
+	static void ready() throws Exception{
+
+		N = Integer.parseInt(br.readLine());
+		arr = new Line[N];
+		root = new int[N];
+		cnt = new int[N];
+		for(int i=0;i<N;i++) {
+			root[i] = i;
+			cnt[i] = 1;
+		}
+
+		for(int i=0;i<N;i++) {
+			nextLine();
+			int x1 = nextInt(), y1 = nextInt(), x2 = nextInt(), y2 = nextInt();
+			arr[i] = new Line(x1,y1,x2,y2);
+		}
+
+	}
+
+	static void solve() throws Exception{
+
+		for(int i=1;i<N;i++) {
+			for(int j=0;j<i;j++) {
+				if(arr[i].intersect(arr[j])) {
+					int x = f(i), y = f(j);
+					if(x != y) {
+						cnt[y] += cnt[x];
+						root[x] = y;
+					}
+				}
+			}
+		}
+
+		int ans = 0, max = 0;
+		boolean[] vis = new boolean[N];
+		for(int i=0;i<N;i++) {
+			int x = f(i);
+			if(vis[x]) continue;
+			vis[x] = true;
+			ans++;
+
+			if(cnt[x] > max) max = cnt[x];
+		}
+		bw.write(ans+"\n"+max);
+
+	}
+
+	static int f(int x) {return x==root[x] ? x : (root[x]=f(root[x]));}
+
+}
+
+```