空间几何题目列表

平面几何

https://www.lanqiao.cn/problems/503/learning/?page=1&first_category_id=1&sort=students_count&name=平面切分

• 解释：
  重点在于线段的去重和交点的去重
• 代码

  #include <iostream>
  #include <set>
  using namespace std;
  typedef pair<double, double> pei;
  const int MAX = 1e5 + 5;
  
  int N;
  double A[MAX];
  double B[MAX];
  struct point{
      double x, y;
      point(double x, double y):x(x), y(y){
  
      }
      bool operator < (const point& p1) const{
          return x < p1.x;
      }
  };
  
  int main()
  {
      // 请在此输入您的代码
      cin >> N;
      for(int i = 0; i < N; i++) {
          cin >> A[i] >> B[i];
      }
      set<pei> st;
      
      int ans = 1;//记得一开始是一个面
      for(int i = 0; i < N; i++) {
          if(st.count(pei(A[i], B[i]))) {
              continue;
          }
          //说明这里的不重合
          int index = 0;
          set<point> pt;
          for(auto it : st) {
              double a = A[i], b = B[i], c = it.first, d = it.second;
              if(a == c) {
                  continue;
              }
              point newp((d - b)/(a - c), (a*d - b*c)/(a - c));
              if(pt.count(newp)) {
                  continue;
              }
              index++;
              pt.insert(newp);
          }
          st.insert(pei(A[i], B[i]));
          ans += index + 1;
      }
      cout << ans;
      return 0;
  
  }