부록 D 2162번 풀이 추가

Appendix D/solutions/2162.cpp

@@ -1,11 +1,76 @@
-// Authored by : BaaaaaaaaaaarkingDog
+// Authored by : uhwan0723
 // Co-authored by : -
-// http://boj.kr/****************
+// http://boj.kr/2104709e50904a80a64a245ab602968e
 #include <bits/stdc++.h>
+#define X first
+#define Y second
 using namespace std;
 
+const int mn = 3005;
+int n, par[mn], sz[mn];
+vector<tuple<int, int, int, int>> lines;
+
+int ccw(pair<int, int> p1, pair<int, int> p2, pair<int, int> p3){
+  int res = p1.X * p2.Y + p2.X * p3.Y + p3.X * p1.Y;
+  res -= p1.Y * p2.X + p2.Y * p3.X + p3.Y * p1.X;
+  if(res > 0) return 1;
+  else if(res < 0) return -1;
+  return 0;
+}
+
+bool isintersect(tuple<int, int, int, int> l1, tuple<int, int, int, int> l2){
+  int l1x1, l1y1, l1x2, l1y2;
+  tie(l1x1, l1y1, l1x2, l1y2) = l1;
+
+  int l2x1, l2y1, l2x2, l2y2;
+  tie(l2x1, l2y1, l2x2, l2y2) = l2;
+
+  pair<int, int> p1 = {l1x1, l1y1}, p2 = {l1x2, l1y2};
+  pair<int, int> p3 = {l2x1, l2y1}, p4 = {l2x2, l2y2};
+
+  int f1 = ccw(p1, p2, p3) * ccw(p1, p2, p4);
+  int f2 = ccw(p3, p4, p1) * ccw(p3, p4, p2);
+
+  if(f1 == 0 && f2 == 0){
+    if(p1 > p2) swap(p1, p2);
+    if(p3 > p4) swap(p3, p4);
+    return p1 <= p4 && p3 <= p2;
+  }
+  return f1 <= 0 && f2 <= 0;
+}
+
+int find(int x){
+  if(par[x] < 0) return x;
+  return par[x] = find(par[x]);
+}
+
+void uni(int x, int y){
+  int u = find(x), v = find(y);
+  if(u == v) return;
+  if(-par[u] < -par[v]) swap(u, v);
+  if(par[u] == par[v]) --par[u];
+  par[v] = u;
+  sz[u] += sz[v];
+}
+
 int main(void){
   ios::sync_with_stdio(0);
   cin.tie(0);
+  cin >> n;
+  fill(par, par+n+5, -1);
+  fill(sz, sz+n+5, 1);
+  for(int i = 0; i < n; ++i){
+    int x1, y1, x2, y2;
+    cin >> x1 >> y1 >> x2 >> y2;
+    lines.push_back({x1, y1, x2, y2});
+  }
+
+  for(int i = 0; i < n; ++i)
+    for(int j = i+1; j < n; ++j)
+      if(isintersect(lines[i], lines[j])) uni(i, j);
 
-}
+  int cnt = 0;
+  for(int i = 0; i < n; ++i)
+    cnt += par[i] < 0;
+  cout << cnt << '\n' << *max_element(sz, sz+n);
+}