POJ 2194 2850 计算几何

//By SiriusRen
#include <cmath>
#include <cstdio>
#include <algorithm>
using namespace std;
int cases,n;
typedef double db;
struct P{db x,y;P(){}P(db X,db Y){x=X,y=Y;}}p[15][15];
bool operator<(P a,P b){return a.x<b.x;}
P operator-(P a,P b){return P(a.x-b.x,a.y-b.y);}
P operator+(P a,P b){return P(a.x+b.x,a.y+b.y);}
db dis(P a){return sqrt(a.x*a.x+a.y*a.y);}
P get(P a,P b){
    P c=b-a;db d=dis(c),p=d/2+2,S=sqrt(p*(p-2)*(p-2)*(p-d)),h=S/d*2;
    c.x/=d,c.y/=d;c=P(-c.y*h,c.x*h);
    return P((a.x+b.x)/2+c.x,(a.y+b.y)/2+c.y);
}
int main(){
    while(scanf("%d",&n)&&n){
        for(int i=1;i<=n;i++)scanf("%lf",&p[n][i].x),p[n][i].y=1;
        sort(p[n]+1,p[n]+1+n);
        for(int i=n-1;i;i--)
            for(int j=1;j<=i;j++)
                p[i][j]=get(p[i+1][j],p[i+1][j+1]);
        printf("%.4lf %.4lf\n",p[1][1].x,p[1][1].y);
    }
}