View Code of Problem 67

#include <stdio.h>

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