题解 | Game of Lines-牛客假日团队赛7K题

Farmer John has challenged Bessie to the following game: FJ has a board with dots marked at  distinct lattice points. Dot i has the integer coordinates and .
Bessie can score a point in the game by picking two of the dots and drawing a straight line between them; however, she is not allowed to draw a line if she has already drawn another line that is parallel to that line. Bessie would like to know her chances of winning, so she has asked you to help find the maximum score she can obtain.

代码如下：

#include<bits/stdc++.h>
using namespace std;
int n,a[201][2],s;
map<double,bool>xl;//开一个以double为下标的bool类型数组
double x;
int main(){
    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>a[i][0]>>a[i][1];//输入
    for(int i=1;i<n;i++)
        for(int j=i+1;j<=n;j++){//两两之间算斜率
            if(a[i][0]==a[j][0]) x=10000;//特判
            else x=(a[i][1]-a[j][1])*1.0/(a[i][0]-a[j][0]);
            if(!xl[x]) s++,xl[x]=1;//如果没有出现过，斜率累加，更新为出现过
        }
    cout<<s;//输出总数
    return 0;
}