I died. (AOJ 0518)

gistfile1.cpp

#include<cstdio>
#include<vector>
#include<algorithm>
#include<set>
#define men(d) (((d.vx*d.vx)+(d.vy*d.vy))/2)
using namespace std;
struct Data{
    short vx,vy,cx,cy;
    Data(short a,short b,short c,short d){
        vx=a;
        vy=b;
        cx=c;
        cy=d;
    }
    Data(){}
};
inline bool operator<(const Data &a,const Data &b){
    if(a.vx<b.vx)return true;
    if(a.vx==b.vx&&a.vy<b.vy)return true;
    if(a.vx==b.vx&a.vy==b.vy&&a.cx<b.cx)return true;
    if(a.vx==b.vx&&a.vy==b.vy&&a.cx==b.cx&&a.cy<b.cy)return true;
    return false;
}
inline bool operator==(const Data &a,const Data &b){
    return a.vx==b.vx&&a.vy==b.vy&&a.cx==b.cx&&a.cy==b.cy;
}
int main(){
    int n;
    for(;;){
        scanf("%d",&n);
        if(n==0)break;
        vector<pair<int,int> > ins(n);
        for(int i=0;i<n;i++){
            int x,y;
            scanf("%d%d",&x,&y);
            ins[i]=make_pair(x,y);
        }
        vector<Data> high,mid,low;
        for(int i=0;i<n;i++){
            for(int j=i+1;j<n;j++){
                int tx=ins[i].first-ins[j].first,ty=ins[i].second-ins[j].second;
                Data d;
                if(tx>=0){
                    d.vx=tx;
                    d.vy=ty;
                }else{
                    d.vx=-tx;
                    d.vy=-ty;
                }
                d.cx=(ins[i].first+ins[j].first)/2;
                d.cy=(ins[i].second+ins[j].second)/2;
                if(d.vy==0)mid.push_back(d);
                else if(d.vy>0)high.push_back(d);
                else low.push_back(d);
            }
        }
        sort(&high[0],&high[0]+high.size());
        sort(&mid[0],&mid[0]+mid.size());
        sort(&low[0],&low[0]+low.size());
        int ma=0;
        for(int i=0;i<mid.size();i++){
            if(binary_search(high.begin(),high.end(),Data(0,mid[i].vx,mid[i].cx,mid[i].cy))||binary_search(low.begin(),low.end(),Data(0,-mid[i].vx,mid[i].cx,mid[i].cy)))ma=max(ma,men(mid[i]));
        }
        for(int i=0;i<high.size();i++){
            if(binary_search(low.begin(),low.end(),Data(high[i].vy,-high[i].vx,high[i].cx,high[i].cy)))ma=max(ma,men(high[i]));
        }
        printf("%d\n",ma);
    }
}