【剑指offer】顺时针打印矩阵

public ArrayList<Integer> (int[][] matrix) {
    int rows = matrix.length;
    int columns = matrix[0].length;
    int start = 0;
    ArrayList<Integer> result = new ArrayList<>();

    while (2 * start < rows && 2 * start < columns){
        printMatrixInCircle(result, matrix, start);
        start++;
    }

    return result;
}

private void printMatrixInCircle(ArrayList<Integer> result, int[][] matrix, int start){
    int rows = matrix.length;
    int columns = matrix[0].length;
    int endX = columns - start - 1;
    int endY = rows - start - 1;

    for (int i = start; i <= endX; i++)
        result.add(matrix[start][i]);

    if (start < endY){
        for (int i = start + 1; i <= endY; i++)
            result.add(matrix[i][endX]);
    }

    if (start < endX && start < endY){
        for (int i = endX - 1; i >= start; i--)
            result.add(matrix[endY][i]);
    }

    if (start < endY - 1 && start < endX){
        for (int i = endY - 1; i > start; i--)
            result.add(matrix[i][start]);
    }
}