View Code of Problem 67

#include <iostream>
using namespace std;

int main(){
  double x1,x2,x3,x4,y1,y2,y3,y4,k1,k2,b1,b2;
  while(scanf("%lf%lf%lf%lf%lf%lf%lf%lf",&x1,&y1,&x2,&y2,&x3,&y3,&x4,&y4)!=EOF){
    if(x1==x2&&x3==x4){
      if(x1==x3)
        printf("Yes\n");
      else
        printf("No\n");
    }
    else{
      k1 = (y2-y1)/(x2-x1);
      k2 = (y4-y3)/(x4-x3);
      b1=y1-k1*x1;
      b2=y3-k2*x3;
      if(k1==k2&&b1!=b2)
        printf("No\n");
      else
        printf("Yes\n");
    }
  }
  return 0;
}