2014 The 5th Shandong Province ACM College Student Programming Competition Painting Cottages

• • Give you a point set that can be divided into several different 2 spaces
  • It can be transformed into a set of points that can have several straight lines
  • Using the idea of ​​3-point collinearity to determine the minimum two points of a straight line through gcd
  • The ideas and codes of the seniors are used. . .

  #include <cstdio>  
  #include <map>  
  #define maxn 1005  
  using namespace std;  
  inline int gcd(int a,int b){return b==0?a:gcd(b,a%b);}  
  struct Point{  
      int x,y;  
      Point(){}  
      inline Point(int _x,int _y){  
          x=_x;  
          y=_y;  
      }  
      inline double lenx(const Point &b)const{  
          return x-b.x;  
      }  
      inline double leny(const Point &b)const{  
          return yb.y;  
      }  
  }P[maxn];  
  int main(){  
      int n;  
      while(~scanf("%d",&n)){  
          for(int i=1;i<=n;++i){  
              int x,y;  
              scanf("%d%d",&x,&y);  
              P[i]=Point(x,y);  
          }  
          int ans=0;  
          for(int i=1;i<=n;++i){  
              map<pair<int ,int>,int> dp;  
              for(int j=i+1;j<=n;++j){  
                      int x=P[i].lenx(P[j]);  
                      int y=P[i].leny(P[j]);  
                      int z=gcd(x,y);  
                  if(!dp[make_pair(x/z,y/z)])dp[make_pair(x/z,y/z)]=++ans;  
              }  
          }  
          printf("%d\n",ans<<1);  
      }  
      return 0;  
  }