View Code of Problem 67

#include <stdio.h>
#include <string.h>
void main() 
{
	int x1, x2, y1, y2, x3, x4, y3, y4;
	while (scanf("%d %d %d %d %d %d %d %d", &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
		{
			float k1 = 1.0 * (y2 - y1) / (x2 - x1);
			float k2 = 1.0 * (y4 - y3) / (x4 - x3);
			if (k1 != k2)
			{
				printf("YES\n");
			}
			else
			{
				float b1 = y2 - k1 * x2;
				float b2 = y3 - k2 * x3;
				if (b1 == b2)
				{
					printf("YES\n");
				}
				else
				{
					printf("NO\n");
				}
			}
		}
	}
}