AOJ 0021 Parallelism
#include <cstdio> int main() { int n; scanf("%d\n", &n); for(int i = 0; i < n; i++){ double x1, y1, x2, y2, x3, y3, x4, y4; scanf("%lf %lf %lf %lf %lf %lf %lf %lf\n", &x1, &y1, &x2, &y2, &x3, &y3, &x4, &y4); puts(((y1 - y2) / (x1 - x2)) == ((y3 - y4) / (x3 - x4)) ? "YES" : "NO"); } return 0; }