poj 1873

哇实验室里正在吵架，爽死了！

wf水题。显然二进制枚举，注意剪枝，val>ans的时候剪一下，不然会tle。然后就没惹。

我老人家一开始写了个

感觉非常垃圾，wa了一发又t了一发。

感觉自己可以退役了

 #include <cstdio>
 #include <cstring>
 #include <cmath>
 #include <iostream>
 #include <iomanip>
 #include <algorithm>
 #include <vector>
 typedef double db;
 #define pdd pair<db,db>
 const db eps = 1e-;
 const db pi = acos(-);
 using namespace std;
 int sign(db k){
     if (k>eps) return ; else if (k<-eps) return -; return ;
 }
 int cmp(db k1,db k2){return sign(k1-k2);}
 struct point{
     db x,y;
     db v,l;
     point operator + (const point &k1) const{return (point){k1.x+x,k1.y+y};}
     point operator - (const point &k1) const{return (point){x-k1.x,y-k1.y};}
     point operator * (db k1) const{return (point){x*k1,y*k1};}
     point operator / (db k1) const{return (point){x/k1,y/k1};}
     bool operator <(const point &k1)const {
         int c=cmp(x,k1.x);
         if(c)return c==-;
         return cmp(y,k1.y)==-;
     }
     db abs(){ return sqrt(x*x+y*y);}
     db dis(point k1){return ((*this)-k1).abs();}
 };
 db cross(point k1,point k2){return k1.x*k2.y-k1.y*k2.x;}
 db dot(point k1,point k2){return k1.x*k2.x+k1.y*k2.y;}
 vector<point> convexHull(vector<point> ps){
     int n = ps.size();if(n<=)return ps;
     sort(ps.begin(),ps.end());
     vector<point> qs(n*);int k=;
     for(int i=;i<n;qs[k++]=ps[i++])
         while (k>&&cross(qs[k-]-qs[k-],ps[i]-qs[k-])<=)--k;
     for(int i=n-,t=k;i>=;qs[k++]=ps[i--])
         while (k>t&&cross(qs[k-]-qs[k-],ps[i]-qs[k-])<=)--k;
     qs.resize(k-);
     return qs;
 }
 int n;
 point p[];
 vector<point> v;
 db res=,sum=1e9;int ans=-;
 void slove(int x){
     v.clear();
     db l1=,val=;
     for(int i=;i<n;i++){
         if(&(x>>i)){//砍了
             l1+=p[i].l;
             val+=p[i].v;
         } else{
             v.push_back(p[i]);
         }
     }
     if(cmp(val,sum)>=)
         return;
     v=convexHull(v);
     db l2=;
     for(int i=;i<v.size();i++){
         l2+=v[i].dis(v[(i+)%v.size()]);
     }
     if(v.size()==)l2=;
     if(cmp(l1,l2)>=){//阔以
         sum=val;
         res=l1-l2;
         ans=x;
     }
 }
 int main(){
     int cas = ;
     while (scanf("%d",&n)&&n){
         cas++;
         for(int i=;i<n;i++){
             scanf("%lf%lf%lf%lf",&p[i].x,&p[i].y,&p[i].v,&p[i].l);
         }
         for(int i=;i<(<<n)-;i++){
             slove(i);
         }
         if(cas>=)printf("\n");
         printf("Forest %d\n",cas);
         printf("Cut these trees:");
         for(int i=;i<n;i++){
             if((ans>>i)&){
                 printf(" %d",i+);
             }
         }
         printf("\nExtra wood: %.2f\n",res);
         res=,sum=1e9;
     }
 }