Write code to parse a simple HTML-like tag structure such as .
Implement parse_html_like(s). Tags contain only letters and digits, have no attributes, and may be nested or appear as siblings. Text between tags should be preserved as strings. Return a nested tree rooted at the single outermost tag, or None if tags are malformed, improperly nested, or if there is not exactly one root element.
Signature: def parse_html_like(s):
def parse_html_like(s):