def find_lec_line(html_lines):
    """Progress the given iterator until just after the next lecture line,
         and return the part of the line at the start of the first
         lecture link.  A lecture line contains a lecture link of the
         form '<a href="lectures/...'."""
    for line in html_lines:
        idx = line.find('"lectures/')
        if idx >= 0:
            return line[idx+1:]
    return None

def split_lecs(line):
    """This line should start with 'lectures/...' """
    end_of_link = line.find('"')
    link = line[:end_of_link]
    line = line[end_of_link+1:]
    next_link = line.find('"lectures/')
    if next_link == -1:
        return [link]
    return [link] + split_lecs(line[next_link+1:])

def find_all_notes(html_lines):
    """Given an iterator over lines of HTML, find all lecture note links"""
    result = []
    lecture_line = find_lec_line(html_lines)
    while lecture_line is not None:
        result += split_lecs(lecture_line)
        lecture_line = find_lec_line(html_lines)
    return result