POJ1873+幾何凸包

簡單凸包+暴力枚舉。

/*幾何凸包+暴力*/#include<algorithm>#include<iostream>#include<string.h>#include<stdlib.h>#include<stdio.h>#include<math.h>#include<queue>#include<stack>#include<map>#include<set>using namespace std;typedef long long int64;//typedef __int64 int64;typedef pair<int64,int64> PII;#define MP(a,b) make_pair((a),(b)) const int inf = 0x3f3f3f3f;const double pi=acos(-1.0);const int dx[]={1,-1,0,0};const int dy[]={0,0,1,-1};const double eps = 1e-8;const int maxm = 1005;const int maxn = 16;struct Point2 {int x,y;double val,len;bool ok;//ok = true 需要去掉的點}pnt[ maxn ];int cur[ maxn ];int cnt_cur;double val_cur,ans1;int best[ maxn ];int cnt_best;double val_best,ans2;double Len1,Len2;struct Point {double x,y;bool operator < ( const Point &t ) const {return y<t.y||( y==t.y&&x<t.x );}}a[ maxn ],res[ maxn ];double xmult( Point sp,Point ep,Point op ){return (sp.x-op.x)*(ep.y-op.y)-(sp.y-op.y)*(ep.x-op.x);}double dist( int i,int j ){return sqrt( (res[i].x-res[j].x)*(res[i].x-res[j].x)+(res[i].y-res[j].y)*(res[i].y-res[j].y) );}int Graham( int n ){int top = 1;sort( a,a+n );if( n==0 ) return 0;else res[0] = a[0];if( n==1 ) return 1;else res[1] = a[1];if( n==2 ) return 2;else res[2] = a[2];for( int i=2;i<n;i++ ){while( top>0 && xmult(res[top],res[top-1],a[i])>=0 )top--;res[ ++top ] = a[i];}int len = top;res[ ++top ] = a[ n-2 ];for( int i=n-3;i>=0;i-- ){while( top!=len && xmult( res[top],res[top-1],a[i])>=0 )top--;res[ ++top ] = a[i];}return top;} bool Solve( int n ){double temp1 = 0;int cc = 0;for( int i=0;i<n;i++ ){  if( pnt[i].ok==false ){  a[ cc ].x = 1.0*pnt[ i ].x;  a[ cc ].y = 1.0*pnt[ i ].y;  cc++;  }  else temp1 += pnt[ i ].len;}int q = cc;cc = Graham( q );double temp2 = 0;res[ cc ] = res[ 0 ];for( int i=0;i<cc;i++ ){temp2 += dist( i,i+1 );}ans1 = temp2;Len1 = temp1;if( temp2<=temp1 ) return true;else return false;}int main(){int n;int Case = 1;while( scanf("%d",&n),n ){if( Case!=1 ) printf("\n");for( int i=0;i<n;i++ ){scanf("%d%d%lf%lf",&pnt[i].x,&pnt[i].y,&pnt[i].val,&pnt[i].len);}int N = (1<<n);ans1 = ans2 = 0;val_best = 9999999999.0;for( int i=0;i<N;i++ ){cnt_cur = 0;val_cur = 0;for( int j=0;j<n;j++ ){if( i&(1<<j) ){cur[ cnt_cur++ ] = j;pnt[ j ].ok = true;val_cur += pnt[ j ].val;}elsepnt[ j ].ok = false;}if( cnt_cur==n ) continue;if( Solve(n)==true ){//printf("Solve\n"); if( val_cur<val_best ){ val_best = val_cur; for( int k=0;k<cnt_cur;k++ ){ best[ k ] = cur[ k ]; } cnt_best = cnt_cur; ans2 = ans1; Len2 = Len1; } else if( val_cur==val_best ){ if( cnt_cur<cnt_best ){ for( int k=0;k<cnt_cur;k++ ){ best[ k ] = cur[ k ]; } cnt_best = cnt_cur; ans2 = ans1; Len2 = Len1; } }}}printf("Forest %d\n",Case++);printf("Cut these trees: ");for( int i=0;i<cnt_best;i++ )printf("%d ",best[i]+1);printf("\n");printf("Extra wood: %.2lf\n",Len2-ans2);}return 0;}