241003 선분 교차 2

static long[] a = new long[2];
static long[] b = new long[2];
static long[] c = new long[2];
static long[] d = new long[2];

public static void main(String[] args) throws Exception {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

	StringTokenizer st = new StringTokenizer(br.readLine());
	a[0] = Integer.parseInt(st.nextToken());
	a[1] = Integer.parseInt(st.nextToken());
	b[0] = Integer.parseInt(st.nextToken());
	b[1] = Integer.parseInt(st.nextToken());

	st = new StringTokenizer(br.readLine());
	c[0] = Integer.parseInt(st.nextToken());
	c[1] = Integer.parseInt(st.nextToken());
	d[0] = Integer.parseInt(st.nextToken());
	d[1] = Integer.parseInt(st.nextToken());

	int n1 = computeCCW(a, b, c) * computeCCW(a, b, d);
	int n2 = computeCCW(c, d, a) * computeCCW(c, d, b);

	if (n1 <= 0 && n2 <= 0) {
		if (n1 == 0 && n2 == 0) {
			boolean condition1 = Math.max(a[0], b[0]) >= Math.min(c[0], d[0]);
			boolean condition2 = Math.min(a[0], b[0]) <= Math.max(c[0], d[0]);
			boolean condition3 = Math.max(a[1], b[1]) >= Math.min(c[1], d[1]);
			boolean condition4 = Math.min(a[1], b[1]) <= Math.max(c[1], d[1]);

			if (condition1 && condition2 && condition3 && condition4) {
				System.out.println(1);
			} else {
				System.out.println(0);
			}
		} else {
			System.out.println(1);
		}
	} else {
		System.out.println(0);
	}
}

static int computeCCW(long[] a, long[] b, long[] c) {
	long temp = a[0] * b[1] + b[0] * c[1] + c[0] * a[1] - (a[1] * b[0] + b[1] * c[0] + c[1] * a[0]);

	if (temp > 0)
		return 1;
	else if (temp == 0)
		return 0;

	return -1;
}

출처:https://www.acmicpc.net/problem/17387