View Code of Problem 67

#include<stdio.h>
int main()
{
	float x1,x2,x3,x4,y1,y2,y3,y4,k1,k2;
	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("NO\n");
			else 
				printf("YES\n");
		}
		else if((x1 == x2 && x3 != x4) || (x1 != x2 && x3 == x4))
		{
			printf("YES\n");
		}  
		else
		{
			k1 = (y2 - y1) / (x2 - x1);
		    k2 = (y4 - y3) / (x4 - x3);
		}
		if(k1 == k2)
		{
			printf("NO\n");
		}
		else
		{
			printf("YES\n");
		}
	}
}