【洛谷P1378】油滴扩展

搜索……

PS一个坑点：r<=0时并不是舍弃这种情况，而是让r=0

（因为每个点都要放一滴油）（读题啊！）

 #include<cstdio>
 #include<cstring>
 #include<cmath>
 #define dd double
 using namespace std;
 const int N=;
 const dd pai=3.1415926535,INF=;
 int flag[N],n;
 dd xx,yy,x2,y2,x[N],y[N];
 //'int y1' redeclared as different kind of symbol,保留字
 dd dx[N][],dy[N][],dis[N][N],r[N],ans;
 void swap(dd &a,dd &b){
     dd tmp=a;
     a=b;
     b=tmp;
 }
 dd min(dd a,dd b){
     return a<b?a:b;
 }
 dd max(dd a,dd b){
     return a>b?a:b;
 }
 void dfs(int step,dd size){
     if (step==n){
         ans=max(ans,size);
         return;
     }
     for (int i=;i<=n;i++){
         if (!flag[i]){
             dd len=min(dx[i][],dx[i][]);
             len=min(len,min(dy[i][],dy[i][]));
             for (int j=;j<=n;j++)
                 if (flag[j]){
                     dd l=dis[i][j]-r[j];
                     if (l>)
                         len=min(len,l);
                     else
                         len=;//***
                 }
             flag[i]=;
             r[i]=len;
             size+=pai*r[i]*r[i];
             dfs(step+,size);
             flag[i]=;
             size-=pai*r[i]*r[i];
         }
     }
 }
 int main(){
     scanf("%d",&n);
     scanf("%lf %lf %lf %lf",&xx,&yy,&x2,&y2);
     for (int i=;i<=n;i++)
         scanf("%lf %lf",&x[i],&y[i]);
     if (xx>x2)
         swap(xx,x2);
     if (yy>y2)
         swap(yy,y2);
     for (int i=;i<=n;i++){
         dx[i][]=x2-x[i];
         dx[i][]=x[i]-xx;
         dy[i][]=y2-y[i];
         dy[i][]=y[i]-yy;
         for (int j=;j<=n;j++){
             int cx=x[i]-x[j];
             int cy=y[i]-y[j];
             dis[i][j]=sqrt(cx*cx+cy*cy);
         }
     }
     ans=;
     dfs(,);
     dd s=(x2-xx)*(y2-yy)-ans;
     int S=s+0.5;
     printf("%d",S);
     return ;
 }

STD