View Code of Problem 67

#include<stdio.h>
void main() 
{
	int x1, x2, x3, x4, y1, y2, y3, y4;
	while (scanf("%f %f %f %f %f %f %f %f", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4) != EOF)
	{
		float tan1 = (y2 - y1) / (x2 - x1);
		float tan2 = (y4 - y3) / (x4 - x3);
		float b1 = y2 - x2 * tan1;
		float b2 = y4 - x4 * tan2;
		if (x1 == x2 && x3 == x4)
		{
			if (x1 == x3)
			{
				printf("YES\n");
			}
			else
			{
				printf("NO\n");
			}
		}
		else 
		{
			if (tan1 == tan2 && b1 != b2)
			{
				printf("YES\n");
			}
			else
			{
				printf("NO\n");
			}
		}
		
	}
}