Date: 2026-06-06
Time: 16:56
goal-parser-interpretation/solution.pyThis file solves LeetCode 1678: Goal Parser Interpretation. It owns a single responsibility: translating a Goal Parser command string by replacing the tokens "G", "()", and "(al)" with "G", "o", and "al" respectively. The function name num_ways is a misnomer — it doesn't count anything. It returns a transformed string.
num_ways(command: str) -> str — The sole function. Takes a command string constrained to the characters G, (, ), a, l and returns the interpreted result. Despite the name suggesting a numeric return, the signature and implementation both return str.
The solution uses chained str.replace() — a greedy left-to-right substitution idiom. This works here because the two replacement targets "()" and "(al)" are unambiguous: "()" is a strict subset prefix of "(al)", but replace matches the exact substring, so replacing "()" first doesn't corrupt "(al)" tokens (the al inside parentheses is preserved until the second replace call strips the wrapping parens). Order matters only if tokens could overlap — here they can't, because "()" won't match inside "(al)".
Imports: None. Pure standard library string operations.
Imported by: The "Imported By" list is misleading — those ~400+ test files don't import *this* solution. They're listed because the repo tooling indexed cross-references broadly. The actual consumer is goal-parser-interpretation/testsolution.py, which imports numways to validate it against test cases.
1. command.replace("()", "o") scans left-to-right, replacing every () with o. The G and (al) tokens pass through unchanged.
2. The intermediate string then undergoes .replace("(al)", "al"), stripping the parentheses from any (al) tokens.
3. The result is returned. No intermediate variables, no iteration, no branching.
For input "G()(al)": step 1 produces "Go(al)", step 2 produces "Goal".
G, (), (al)). The function does no validation — malformed input like "(" passes through unchanged.str.replace is non-overlapping and left-to-right, so the two replacements are independent and commutative for this specific token set.None. No validation, no exceptions. Invalid input silently produces garbage output. This is standard for LeetCode solutions where inputs are guaranteed well-formed by the problem constraints.
O(n) time and space where n = len(command). Each replace scans the full string once and allocates a new string.