poj2007极角排序

裸的极角排序，但是要把0，0放在第一个（话说这题题目真是巨长，废话也多。。。）

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pi acos(-1.0)
#define ll long long
#define mod 1000000007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#pragma comment(linker, "/STACK:1024000000,1024000000")

using namespace std;

const double g=10.0,eps=1e-9;
const int N=100+10,maxn=500+100,inf=0x3f3f3f;

struct point{
    double x,y;
}p[N];
double dis(point p1,point p2)
{
    return sqrt((p1.x-p2.x)*(p1.x-p2.x)+(p1.y-p2.y)*(p1.y-p2.y));
}
double dir(point p1,point p2,point p3)
{
    return (p3.x-p1.x)*(p2.y-p1.y)-(p3.y-p1.y)*(p2.x-p1.x);
}
bool comp(point p1,point p2)
{
    double te=dir(p[0],p1,p2);
    if(te<0)return 1;
    if(te==0&&dis(p[0],p1)<dis(p[0],p2))return 1;
    return 0;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    int cnt=0;
    while(cin>>p[cnt].x>>p[cnt].y){
        //if(p[cnt].x==-1&&p[cnt].y==-1)break;
        cnt++;
    }
    int pos;
    for(int i=0;i<cnt;i++)
        if(p[i].x==0&&p[i].y==0)
            pos=i;
    swap(p[0],p[pos]);
    sort(p+1,p+cnt,comp);
    for(int i=0;i<cnt;i++)
        cout<<"("<<p[i].x<<","<<p[i].y<<")"<<endl;
    return 0;
}      

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