URL Query-String Parser

Given a URL string, parse its query portion into a dictionary. Handle keys without values, repeated keys (collect into a list), and URL-encoded characters (`%26`, `%3D`, …) via an unquote helper. Requirements The query string starts after the first ?. Each parameter is key=value, separated by &. If a key appears without =, treat the value as True (or empty string, clarify with the interviewer). If a key appears multiple times, collect the values into a list. Decode percent-encoded bytes — the interviewer typically hands the candidate an unquote(s) helper rather than asking them to implement it. If the URL has no ?, return an empty dict. Examples: "?a=b&c=d" -> {"a": "b", "c": "d"} "?sd" -> {"sd": True} "?a=b&a=c&a=d" -> {"a": ["b", "c", "d"]} "?key=hello%20world" -> {"key": "hello world"} A typed-value variant has also appeared, where values may be Integer, String, Boolean, or List, and a bare !field (or a bare key) resolves to a boolean: "?key1=1&key1=\"abc\"&key2=value1&!isBooleanField" -> {"key1": ["1", "abc"], "key2": "value1", "isBooleanField": "true"} Notes Single-pass split: query = url.split("?", 1)[1] if ? exists; parts = query.split("&"). Repeated-key handling: track a dict[str, str | list[str]]; on the second occurrence promote the value to a list, on the third+ append. Decoding policy: apply unquote to both key and value after splitting on & and = — applying it before splitting will corrupt encoded = / & inside values. Invalid-URL handling: the interviewer typically asks for graceful behavior — drop empty segments, treat trailing & as no-op. Clarify the no-value convention upfront (some prompts want True, others empty string, others None). Value typing varies by interviewer: some want raw strings, others want values coerced to Integer / String / Boolean / List. Clarify the expected types and the bare-key / !-prefix boolean convention before coding. The unquote helper is not always a freebie: a later follow-up can ask the candidate to implement it — scan for %, parse the two hex digits, emit the decoded character. Be ready to write it by hand. Preparation Implement in 10 minutes cold, then layer on repeated-key and decoding. Write 4 tests: simple, no-value key, repeated key, encoded value. Prepare a one-liner for the follow-up "what about fragments (#section)?" — strip the fragment before parsing the query. Pair-prep with text-justification-table — both fit the same fast phone-screen slot.