View Code of Problem 67

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