From fd4da9e05ccbb977e99cafff22cf364e0cf57adf Mon Sep 17 00:00:00 2001
From: yuyu0830 <yuyu0830@naver.com>
Date: Tue, 20 Aug 2024 18:16:45 +0900
Subject: [PATCH] =?UTF-8?q?24/08/20=20=EC=84=A0=EB=B6=84=20=EA=B7=B8?=
 =?UTF-8?q?=EB=A3=B9?=
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---
 yuyu0830/README.md                           |   1 +
 "yuyu0830/\354\210\230\355\225\231/2162.cpp" | 123 +++++++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 "yuyu0830/\354\210\230\355\225\231/2162.cpp"

diff --git a/yuyu0830/README.md b/yuyu0830/README.md
index 96f05e2..d1b6aeb 100644
--- a/yuyu0830/README.md
+++ b/yuyu0830/README.md
@@ -23,4 +23,5 @@
 | 19차시 | 2024.07.12 |  재귀  | [우수마을](https://www.acmicpc.net/problem/1949)  | - |
 | 20차시 | 2024.07.22 |  LIS  | [가장 긴 증가하는 부분 수열 5](https://www.acmicpc.net/problem/14003)  | - |
 | 21차시 | 2024.07.23 |  수학  | [1의 개수 세기](https://www.acmicpc.net/problem/9527)  | - |
+| 26차시 | 2024.08.20 |  기하  | [선분 그룹](https://www.acmicpc.net/problem/2162)  | - |
 ---
\ No newline at end of file
diff --git "a/yuyu0830/\354\210\230\355\225\231/2162.cpp" "b/yuyu0830/\354\210\230\355\225\231/2162.cpp"
new file mode 100644
index 0000000..058f9a1
--- /dev/null
+++ "b/yuyu0830/\354\210\230\355\225\231/2162.cpp"
@@ -0,0 +1,123 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+
+using namespace std;
+
+struct Point {
+    int x, y;
+    void set(int X, int Y) {
+        x = X;
+        y = Y;
+    }
+
+    bool operator== (const Point t) {
+        return x == t.x && y == t.y;
+    }
+};
+
+struct Line {
+    Point a, b;
+
+    void set(int x1, int y1, int x2, int y2) {
+        bool e;
+
+        // x가 작은 순, 같다면 y가 큰 순
+        // 사분면에서 왼쪽 위 점을 우선
+        if (x1 != x2) e = x1 < x2;
+        else e = y1 > y2;
+        
+        a.x = e ? x1 : x2;
+        a.y = e ? y1 : y2;
+        b.x = e ? x2 : x1;
+        b.y = e ? y2 : y1;
+    }
+};
+
+
+// CCW
+Line arr[3001];
+bool visited[3001] = {0, };
+
+int CCW(Point a, Point b, Point c) {
+    int t1 = a.x * b.y + b.x * c.y + c.x * a.y;
+    int t2 = a.y * b.x + b.y * c.x + c.y * a.x;
+
+    int s = t1 - t2;
+
+    if (s > 0) return 1;
+    else if (!s) return 0;
+    else return -1;
+}
+
+bool isIntersect(Line l1, Line l2) {
+    Point p1 = l1.a;
+    Point p2 = l1.b;
+    Point p3 = l2.a;
+    Point p4 = l2.b;
+
+    if (p1 == p3 || p1 == p4 || p2 == p3 || p2 == p4) return true;
+
+    int t1 = CCW(p1, p2, p3) * CCW(p1, p2, p4); // l1 기준
+    int t2 = CCW(p3, p4, p1) * CCW(p3, p4, p2); // l2 기준
+
+    // 두 직선이 일직선 상에 존재하면
+    // 기울기가 0 혹은 무한인 경우 || 겹치는 경우
+    if (!t1 && !t2) {
+        bool x = (p1.x == p3.x && p2.x == p4.x) || (p1.x <= p4.x != p2.x <= p3.x);
+        bool y = (p1.y == p3.y && p2.y == p4.y) || (p1.y >= p4.y != p2.y >= p3.y);
+
+        return x && y;
+    }
+
+    return t1 <= 0 && t2 <= 0;
+}
+
+// union find
+int parent[3001] = {0, };
+int count[3001] = {0, };
+
+int find(int v) {
+    if (parent[v] == v) return v;
+    return parent[v] = find(parent[v]);
+}
+
+void merge(int x, int y) { 
+    parent[find(min(x, y))] = find(max(x, y));
+}
+
+int main() {
+    int n; cin >> n;
+
+    for (int i = 0; i < n; i++) {
+        int a, b, c, d; cin >> a >> b >> c >> d;
+        arr[i].set(a, b, c, d);
+
+        parent[i] = i;
+    }
+
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < i; j++) {
+            // i번째 Line는 0 ~ i - 1번째 Line까지 겹치는지 확인
+            // 겹치면 Union 해버리기
+            if (isIntersect(arr[i], arr[j])) 
+                merge(i, j);
+        }
+    }
+    
+    // 겹침 여부가 뒤에 결정될 수도 있기 때문에 나중에 몰아서 개수 연산
+    for (int i = 0; i < n; i++) 
+        ::count[find(i)]++;
+
+    int cnt = 0, maxCnt = 0;
+
+    // 개수 갱신
+    for (int i = 0; i < n; i++) {
+        if (::count[i]) {
+            cnt++;
+            maxCnt = max(maxCnt, ::count[i]);
+        } 
+    }
+
+    printf("%d\n%d\n", cnt, maxCnt);
+}
\ No newline at end of file