P2665 [USACO08FEB]连线游戏Game of Lines

传送门

不平行就是直线斜率不同

枚举所有两点的斜率，对平行坐标轴的线特殊考虑

离散化一下就好了

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
using namespace std;
inline int read()
{
    int x=0,f=1; char ch=getchar();
    while(ch<'0'||ch>'9') { if(ch=='-') f=-1; ch=getchar(); }
    while(ch>='0'&&ch<='9') { x=(x<<1)+(x<<3)+(ch^48); ch=getchar(); }
    return x*f;
}
const int N=4e4+7;
const double INF=2e9+7;
int n,pos[207][2],cnt,ans;
double k[N];
int main()
{
    n=read();
    for(int i=1;i<=n;i++) pos[i][0]=read(),pos[i][1]=read();
    for(int i=1;i<=n;i++)
        for(int j=i+1;j<=n;j++)
        {
            cnt++;
            if(pos[i][0]==pos[j][0]) { k[cnt]=INF; continue; }
            if(pos[i][1]==pos[j][1]) { k[cnt]=0; continue; }
            k[cnt]=(double)(pos[i][1]-pos[j][1])/(double)(pos[i][0]-pos[j][0]);
        }
    sort(k+1,k+cnt+1);
    ans=1;
    for(int i=2;i<=cnt;i++) if(k[i]!=k[i-1]) ans++;
    printf("%d",ans);
    return 0;
}