poj1873The Fortified Forest

链接

居然是WF的水题~

二进制枚举砍哪些树，剩余的树围成一个凸包。

因为传数组WA了两发，忘记修改排序数组中的p[0];

 #include <iostream>
 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 #include<stdlib.h>
 #include<vector>
 #include<cmath>
 #include<queue>
 #include<set>
 using namespace std;
 #define N 20
 #define LL long long
 #define INF 0xfffffff
 const double eps = 1e-;
 const double pi = acos(-1.0);
 const double inf = ~0u>>;
 struct point
 {
     int x,y;
     int vi,li;
     point(int x=,int y=):x(x),y(y){}
 }p[N],q[N],ch[N];
 int o[N],f[N];
 typedef point pointt;
 pointt operator -(point a,point b)
 {
     return point(a.x-b.x,a.y-b.y);
 }
 int dcmp(double x)
 {
     if(fabs(x)<eps) return ;
     return x<?-:;
 }
 double cross(point a,point b)
 {
     return 1.0*a.x*b.y-a.y*b.x;
 }
 double mul(point p0,point p1,point p2)
 {
     return cross(p1-p0,p2-p0);
 }
 double dis(point a)
 {
     return sqrt(1.0*a.x*a.x+a.y*a.y);
 }
 bool cmp(point a,point b)
 {
     if(dcmp(mul(q[],a,b))==)
         return dis(a-q[])<dis(b-q[]);
     else
         return dcmp(mul(q[],a,b))>;
 }
 double Graham(int n)
 {
     if(n<=) return ;
     if(n==) return *dis(q[]-q[]);
     int i,k = ,top;
     point tmp;
     for(i =  ; i < n; i++)
     {
         if(q[i].y<q[k].y||(q[i].y==q[k].y&&q[i].x<q[k].x))
             k = i;
     }
     if(k!=)
     {
         tmp = q[];
         q[] = q[k];
         q[k] = tmp;
     }
     sort(q+,q+n,cmp);
     ch[] = q[];
     ch[] = q[];
     top = ;
     for(i = ; i < n ; i++)
     {
         while(top>&&dcmp(mul(ch[top-],ch[top],q[i]))<)
             top--;
         top++;
         ch[top] =q[i];
     }
     ch[top+] = ch[];
     double len = ;
     for(i =  ; i <= top ; i++)
     len+=dis(ch[i]-ch[i+]);
     return len;
 }
 int main()
 {
     int n,i,j,g;
     int kk = ;
     while(scanf("%d",&n)&&n)
     {
         for(i =  ; i <n ;i++)
         scanf("%d%d%d%d",&p[i].x,&p[i].y,&p[i].vi,&p[i].li);
         int num;
         int ans = INF;
         double res = ;
         for(i =  ; i < (<<n) ; i++)
         {
             g = ;
             int gg = ;
             int tv = ;
             double tlen = ;
             for(j =  ;j < n; j++)
             {
                 if((<<j)&i)
                 {
                     f[gg++] = j;
                     tlen+=p[j].li;
                     tv += p[j].vi;
                 }
                 else q[g++] = p[j];
             }
             double len = Graham(g);
             if(dcmp(tlen-len)>=)
             {
                 if(ans>tv||(ans==tv&&num>gg))
                 {
                     ans = tv;
                     num = gg;
                     res = tlen-len;
                     //cout<<len<<" "<<i<<endl;

                     for(j =  ; j < gg ; j++)
                     o[j] = f[j]+;
                 }
             }
         }
         if(kk) puts("");
         printf("Forest %d\n",++kk);
         printf("Cut these trees: ");
         for(i = ; i < num-; i++)
         printf("%d ",o[i]);
         if(num)
         printf("%d\n",o[num-]);
         printf("Extra wood: %.2f\n",res);
     }
     return ;
 }