View Code of Problem 67

#include <iostream>
#include <cstdio>
using namespace std;
int main(){
    double x1,x2,x3,x4;
    double y1,y2,y3,y4;
    double k1,k2,b1,b2;
    while(cin>>x1>>y1>>x2>>y2>>x3>>y3>>x4>>y4){
        if(x1!=x2&&x3!=x4){
            k1=(y1-y2)/(x1-x2);
            k2=(y3-y4)/(x3-x4);
            b1=y1-k1*x1;
            b2=y3-k2*x3;
            if(k1==k2&&b1!=b2)
                cout<<"NO"<<endl;
            else
                cout<<"YES"<<endl;
        }
        if(x1==x2&&x3==x4){
            if(x1==x3)
                cout<<"YES";
            else
                cout<<"NO";
        }
    }
    return 0;
}