230421 교점에 별 만들기

public String[] solution(int[][] line) {
    List<long[]> intersections = new ArrayList<>();
    long minX = Long.MAX_VALUE;
    long maxX = Long.MIN_VALUE;
    long minY = Long.MAX_VALUE;
    long maxY = Long.MIN_VALUE;

    for (int i = 0; i < line.length; i++) {
        long a = line[i][0];
        long b = line[i][1];
        long e = line[i][2];

        for (int j = i + 1; j < line.length; j++) {
            long c = line[j][0];
            long d = line[j][1];
            long f = line[j][2];
            long temp = a * d - b * c;

            if (temp == 0)
                continue;

            double x = (b * f - e * d) / (double) temp;
            double y = (e * c - a * f) / (double) temp;

            if (x == Math.ceil(x) && y == Math.ceil(y)) {
                long xLong = (long) x;
                long yLong = (long) y;
                intersections.add(new long[] { xLong, yLong });
                minX = Math.min(minX, xLong);
                maxX = Math.max(maxX, xLong);
                minY = Math.min(minY, yLong);
                maxY = Math.max(maxY, yLong);
            }
        }
    }

    boolean[][] answerTemp = moveAnswer(intersections, minX, maxX, minY, maxY);

    return makeAnswer(answerTemp);
}


private boolean[][] moveAnswer(List<long[]> intersections, long minX, long maxX, long minY, long maxY) {
    boolean[][] answerTemp = new boolean[(int) (maxY - minY + 1)][(int) (maxX - minX + 1)];

    for (long[] intersection : intersections) {
        int x = (int) (intersection[0] - minX);
        int y = (int) (maxY - intersection[1]);
        answerTemp[y][x] = true;
    }
    return answerTemp;
}

private String[] makeAnswer(boolean[][] answerTemp) {
    String[] answer = new String[answerTemp.length];
    for (int i = 0; i < answer.length; i++) {
        StringBuilder sb = new StringBuilder();
        for (boolean b : answerTemp[i]) {
            if (b) {
                sb.append("*");
                continue;
            } 
                sb.append(".");
        }
        answer[i] = sb.toString();
    }
    return answer;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/87377