View Code of Problem 67

#include <stdio.h>
using namespace std;
int main() {
    double x1,x2,x3,x4,y1,y2,y3,y4;
    while(~scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2)){
       scanf("%lf%lf%lf%lf",&x3,&y3,&x4,&y4);
        if( x1 != x2 && x3 != x4 ){
            double k1 = 1.0*(y2-y1)/(x2-x1);
            double k2 = 1.0*(y4-y3)/(x4-x3);
            if( k1 != k2 ){
                printf("Yes\n");
            }else if( y1 - k1*x1 != y3-k2*x3 ){
                printf("No\n");
            }else{
                printf("Yes\n");
            }
        }else if(x1 == x2 && x3 == x4 && x1 != x3){
           printf("No\n");
       }else{
           printf("Yes\n");
       }
   }
    return 0;
}