hoj 13781 Wedding Sel?e

#include <iostream>
#include <algorithm>
#include <stdio.h>
#include <queue>
#include <limits.h>
#include <string.h>
#include <vector>
#include <map>
#include <math.h>
#define LL unsigned long long
#define INF 2100000000
#define fi first
#define se second
#define lowbit(x) (x&(-x))
#define eps 5e-7
using namespace std;
const int maxn=(int)1e2 +30;
const int MOD=(int)1e9+10;
const double PI=acos(-1.0) ;
int sgn(double x){return (x>eps)-(x<-eps);}
template<class T>inline void MAX(T &a,T b){if(a<b)a=b;}
template<class T>inline void MIN(T &a,T b){if(a>b)a=b;}
struct point {
    double x,y;
    point(){}
    point(double x,double y):x(x),y(y){}

    void input(){scanf("%lf%lf",&x,&y);}
    void output(){printf("%.6lf %.6lf\n",(sgn(x)==0)? 0.0:x,(sgn(y)==0)? 0.0:y); }
    point rotate(double a){return point(x*cos(a)-y*sin(a),x*sin(a)+y*cos(a));}
    //应创立新的点而不是在原有点上更改****important
};
point p[maxn];
double area(point &a,point &b,point &c){
    return fabs(0.5*(a.x*b.y+a.y*c.x+b.x*c.y-b.y*c.x-a.y*b.x-a.x*c.y));
}
double angle(point &a,point &b){
    return -atan2(a.y-b.y,a.x-b.x);// atan2定义很棒
}
double ar[maxn];
int main(){
#ifdef shuaishuai
	freopen("C:\\Users\\hasee\\Desktop\\a.txt","r",stdin);
	//freopen("C:\\Users\\hasee\\Desktop\\b.txt","w",stdout);
#endif
    int t,kas=1;
    int n;
    scanf("%d",&t);
    while(t--){
        scanf("%d",&n);
        p[0].input();p[1].input();
        ar[0]=ar[1]=0.0;
        for(int i=2;i<n;i++){
            p[i].input();
            ar[i]=ar[i-1]+area(p[i],p[i-1],p[0]);
        }
        double tot=ar[n-1];
        int mid=2;
        while(mid<n&&ar[mid]*2.0<tot)mid++;
//        printf("mid :%d\n",mid);
        double arl=tot*0.5-ar[mid-1 ];
        point L=p[mid-1],R=p[mid];
        double l=arl/(ar[mid]-ar[mid-1]);
        point m;
        m.x=L.x+l*(R.x-L.x);m.y=L.y+l*(R.y-L.y);
        double theta=angle(m,p[0])-0.5*PI; //-0.5PI就是旋转到Y负的角度
//        m.output();
//        printf("theta :%.3lf\n",theta);
        printf("Case %d:\n",kas);kas++;
//        for(int i=0;i<n;i++)p[i].output();
        for(int i=0;i<n;i++){
            (p[i].rotate(theta)).output();
        }
    }

	return 0;
}