View Code of Problem 67

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>
#include<math.h>
void main() {
	float x1, y1, x2, y2, x3, y3, x4, y4;
	while(scanf("%f%f%f%f", &x1, &y1, &x2, &y2)!=EOF)
	{
		scanf("%f%f%f%f", &x3, &y3, &x4, &y4); 
		if (x1 == x2 && x3 == x4) {
			if (x1 == x3) {
				printf("YES\n");
			}
			else {
				printf("NO\n");
			}
		}
		else {
			float k1, k2;
			k1 = (y2 - y1) / (x2 - x1);
			k2 = (y4 - y3) / (x4 - x3);
			if (k1 != k2) {
				printf("YES\n");
			}
			else {
				printf("NO\n");
			}
		}
	}
}