凸包模板 POJ1873

// 凸包模板 POJ1873
// n=15所以可以按位枚举求凸包，再记录数据

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <math.h>
using namespace std;
#define LL long long
typedef pair<int,int> pii;
const double inf = 0x3f3f3f3f;
const LL MOD =100000000LL;
const int N =110;
#define clc(a,b) memset(a,b,sizeof(a))
const double eps = 1e-8;
void fre() {freopen("in.txt","r",stdin);}
void freout() {freopen("out.txt","w",stdout);}
inline int read() {int x=0,f=1;char ch=getchar();while(ch>'9'||ch<'0') {if(ch=='-') f=-1; ch=getchar();}while(ch>='0'&&ch<='9') {x=x*10+ch-'0';ch=getchar();}return x*f;}

int sgn(double x){
    if(fabs(x) < eps)return 0;
    if(x < 0)return -1;
    else return 1;
}

struct Point{
    double x,y;
    Point(){}
    Point(double _x,double _y){
        x = _x;y = _y;
    }
    Point operator -(const Point &b)const{
        return Point(x - b.x,y - b.y);
    }
    double operator ^(const Point &b)const{
        return x*b.y - y*b.x;
    }
    double operator *(const Point &b)const{
        return x*b.x + y*b.y;
    }
    friend bool operator<(const Point &a,const Point &b){
        if(fabs(a.y-b.y)<eps) return a.x<b.x;
        return a.y<b.y;
    }
    friend double dis2(Point a){
        return a.x*a.x+a.y*a.y;
    }
};

double dis(Point a,Point b){
    return sqrt(dis2(a-b));
}
double mult(Point a,Point b,Point o){
    return (a.x-o.x)*(b.y-o.y)>=(b.x-o.x)*(a.y-o.y);
}

Point P[16];
double v[16],l[16];

double graham(Point p[],int n,Point q[]){
     int top=1;
     sort(p,p+n);
     if(n==0) return 0;
     q[0]=p[0];
     if(n==1) return 0;
     q[1]=p[1];
     if(n==2) return dis(p[0],p[1])*2;
     q[2]=p[2];
     for(int i=2;i<n;i++){
         while(top&&(mult(p[i],q[top],q[top-1]))) top--;
         q[++top]=p[i];
     }
     int len=top;
     q[++top]=p[n-2];
     for(int i=n-3;i>=0;i--){
         while(top!=len&&(mult(p[i],q[top],q[top-1]))) top--;
         q[++top]=p[i];
     }
     double c=dis(q[0],q[top-1]);
     for(int i=0;i<top-1;i++)
        c+=dis(q[i],q[i+1]);
    return c;
}

int n;
int b[16],a[16];
Point p[16],ch[16];
int main(){
    int cas=1;
    while(~scanf("%d",&n),n){
        for(int i=0;i<n;i++){
            double x,y;
            scanf("%lf%lf%lf%lf",&x,&y,&v[i],&l[i]);
            P[i]=Point(x,y);
        }
        int k,cnt;
        double ans=0;
        int minn_cnt=11111;
        double sum,len,minn=inf;
        for(int st=0;st<(1<<n);st++){
            sum=0,len=0,k=0,cnt=0;

            for(int i=0;i<n;i++){
               if(st&(1<<i)){
                   sum+=v[i];
                   len+=l[i];
                   b[++cnt]=i+1;
               }
               else{
                  p[k++]=P[i];
               }
            }
            double lenn=graham(p,k,ch);
            if(lenn>len) continue;
            if(sum<minn||(sum==minn&&cnt<minn_cnt)){
                minn=sum;
                minn_cnt=cnt;
                ans=len-lenn;
                for(int i=1;i<=cnt;i++){
                    a[i]=b[i];
                }
            }
        }
        printf("Forest %d
",cas++);
        printf("Cut these trees:");
        for(int i=1;i<=minn_cnt;i++){
            printf(" %d",a[i]);
        }
        printf("
");
        printf("Extra wood: ");
        printf("%.2f
",ans);
        printf("
");
    }
    return 0;
}