250525 선분 교차 3

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

	StringTokenizer st = new StringTokenizer(br.readLine(), " ");
	double x1 = Double.parseDouble(st.nextToken());
	double y1 = Double.parseDouble(st.nextToken());
	double x2 = Double.parseDouble(st.nextToken());
	double y2 = Double.parseDouble(st.nextToken());

	st = new StringTokenizer(br.readLine(), " ");
	double x3 = Double.parseDouble(st.nextToken());
	double y3 = Double.parseDouble(st.nextToken());
	double x4 = Double.parseDouble(st.nextToken());
	double y4 = Double.parseDouble(st.nextToken());

	double den = (y2 - y1) * (x4 - x3) - (y4 - y3) * (x2 - x1);

	if (Double.compare(den, 0) == 0) {
		double check = x1 * (y2 - y1) * (x4 - x3) - x3 * (y4 - y3) * (x2 - x1) + (y3 - y1) * (x2 - x1) * (x4 - x3);
		if (Double.compare(check, 0) != 0) {
			System.out.println(0);
		} else {
			if ((x1 < x3 && x2 < x3 && x1 < x4 && x2 < x4) ||
					(x1 > x3 && x2 > x3 && x1 > x4 && x2 > x4) ||
					(y1 < y3 && y2 < y3 && y1 < y4 && y2 < y4) ||
					(y1 > y3 && y2 > y3 && y1 > y4 && y2 > y4)) {
				System.out.println(0);
			} else if ((x1 == x3 && x2 < x1 && x4 > x3) || (x1 == x3 && x2 > x1 && x4 < x3) ||
					(y1 == y3 && y2 < y1 && y4 > y3) || (y1 == y3 && y2 > y1 && y4 < y3)) {
				System.out.println(1);
				System.out.println(x1 + " " + y1);
			} else if ((x1 == x4 && x2 < x1 && x3 > x4) || (x1 == x4 && x2 > x1 && x3 < x4) ||
					(y1 == y4 && y2 < y1 && y3 > y4) || (y1 == y4 && y2 > y1 && y3 < y4)) {
				System.out.println(1);
				System.out.println(x1 + " " + y1);
			} else if ((x2 == x3 && x1 < x2 && x4 > x3) || (x2 == x3 && x1 > x2 && x4 < x3) ||
					(y2 == y3 && y1 < y2 && y4 > y3) || (y2 == y3 && y1 > y2 && y4 < y3)) {
				System.out.println(1);
				System.out.println(x2 + " " + y2);
			} else if ((x2 == x4 && x1 < x2 && x3 > x4) || (x2 == x4 && x1 > x2 && x3 < x4) ||
					(y2 == y4 && y1 < y2 && y3 > y4) || (y2 == y4 && y1 > y2 && y3 < y4)) {
				System.out.println(1);
				System.out.println(x2 + " " + y2);
			} else {
				System.out.println(1);
			}
		}
	} else {
		boolean separated1 = ((y3 - y4) * (x1 - x3) - (x3 - x4) * (y1 - y3)) *
				((y3 - y4) * (x2 - x3) - (x3 - x4) * (y2 - y3)) > 0;
		boolean separated2 = ((y1 - y2) * (x3 - x1) - (x1 - x2) * (y3 - y1)) *
				((y1 - y2) * (x4 - x1) - (x1 - x2) * (y4 - y1)) > 0;
		if (separated1 || separated2) {
			System.out.println(0);
		} else {
			System.out.println(1);
			double x = (x1 * (y2 - y1) * (x4 - x3) - x3 * (y4 - y3) * (x2 - x1) + (y3 - y1) * (x2 - x1) * (x4 - x3))
					/ den;
			double y = (y1 * (x2 - x1) * (y4 - y3) - y3 * (x4 - x3) * (y2 - y1) + (x3 - x1) * (y2 - y1) * (y4 - y3))
					/
					((x2 - x1) * (y4 - y3) - (x4 - x3) * (y2 - y1));
			System.out.println(x + " " + y);
		}
	}
}

출처:https://www.acmicpc.net/problem/20149