polygon programming with ease.txt

以前ACM在哈工程HRBEU做的一些简单题目

#include "iostream.h"
#include "stdio.h"
int main()
{
    double x[200],y[200],xs[200],ys[200],tx,ty;
    int n,i,k;
    while(cin>>n)
    {
      for(i=0;i<n;i++)cin>>x[i]>>y[i];
      tx=ty=0;
      k=1;
      for(i=0;i<n;i++){tx+=k*x[i];ty+=k*y[i];k*=-1;}
      xs[0]=tx;
      ys[0]=ty;
      for(i=1;i<n;i++){xs[i]=2*x[i-1]-xs[i-1];ys[i]=2*y[i-1]-ys[i-1];}
      cout<<n;
      for(i=0;i<n;i++)printf(" %.6lf %.6lf",xs[i],ys[i]);
      cout<<endl;
    }
    return 0;
}