View Code of Problem 67

#include <stdio.h>
#include <math.h>
#include <string.h>
int main()
{
	float x1, y1, x2, y2, x3, y3, x4, y4, k1, k2, b1, b2;
	while (scanf("%f %f %f %f %f %f %f %f", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4) != EOF) {
		k1 = (y2 - y1) / (x2 - x1);
		k2 = (y4 - y3) / (x4 - x3);
		b1 = y1 - k1 * x1;
		b2 = y3 - k2 * x3;
		if (x1 == x2 && x3 == x4 && x1 != x3) {
			printf("No\n");
		}
		else if (k1 == k2 && b1 != b2) {
			printf("No\n");
		}
		else {
			printf("Yes\n");
		}
	}
	return 0;
}