油滴扩散

链接
写完了，犯了个很瓜的错
。。。。dfs的时候没有存r

题解嘛爆搜没有什么好提的

写的时候借鉴了第二篇题解

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#define db double
using namespace std;
db a[100][3]={0},s,x,y,x1,yy;
db r[1010],ans=0.0;
int vis[1000101]={0},n;
double dis(db xx,db yy,db xx1,db yy1){
    return sqrt((xx-xx1)*(xx-xx1)+(yy-yy1)*(yy-yy1));
}
double minn(int k){
    for(int i=1;i<=n;i++)
        if(i!=k&&vis[i]==1)
            if(r[i]>dis(a[i][1],a[i][2],a[k][1],a[k][2])) return 0;
    double dist=0;
    double ans=min(min(abs(a[k][1]-x),abs(a[k][1]-x1)),min(abs(a[k][2]-y),abs(a[k][2]-yy)));
    for(int i=1;i<=n;i++)
        if(i!=k&&vis[i]==1){
            dist=dis(a[i][1],a[i][2],a[k][1],a[k][2])-r[i];
            ans=min(ans,dist);
        }
    return ans;
}
void dfs(int x,db y){
	if(x==n){
		ans=max(y,ans);
		return;
	}
	for(int i=1;i<=n;i++){
		if(!vis[i]){
			vis[i]=1;
			db lala=minn(i);
                         r[i]=lala;
			dfs(x+1,y+3.14*lala*lala);
			r[i]=0;
			vis[i]=0;
		}
	}
}
int main(){
    scanf("%d",&n);
    scanf("%lf%lf%lf%lf",&x,&y,&x1,&yy);
    s=abs(x-x1)*abs(y-yy);
    for(int i=1;i<=n;i++)
		scanf("%lf%lf",&a[i][1],&a[i][2]);
    dfs(0,0.0);
   	printf("%0.0f",s-ans);
    return 0;
}