hdu 6127 : Hard challenge (2017 多校第七场 1008）（计算几何）

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;

const long double pi=3.14159265358979323846264338327950288L;
const long double eps=1e-15;

struct point
{
    int x,y;
    LL val;
    long double j;
    bool operator <(const point rhs)
    {
        return j<rhs.j;
    }
}p[100005];

int n;
LL s[100005];

LL sum(int l,int r)
{
//    if(l>r) puts("========================");
    return s[r]-s[l]+p[l].val;
}

int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        memset(s,0,sizeof(s));
        LL ans=0;
        scanf("%d",&n);
        for(int i=0;i<n;i++)
        {
            scanf("%d%d%lld",&p[i].x,&p[i].y,&p[i].val);
            p[i].j=atan2l(p[i].y,p[i].x);
        }
        sort(p,p+n);
        for(int i=0;i<n;i++) p[i+n]=p[i],p[i+n].j+=2*pi;
        s[0]=p[0].val;
        for(int i=1;i<2*n;i++) s[i]=s[i-1]+p[i].val;
        for(int l=0,r=0;l<n;l++)    //使用双指针 l,r
        {
            while(p[r+1].j<p[l].j+pi) r++;
            LL v1=sum(l,r);
            LL v2=s[n-1]-v1;
            ans=max(ans,v1*v2);
        }
        printf("%lld\n",ans);
    }
}