Pattern Matching With Conditions (Wildcards and Rules)

Conditional matching means not every character must be equal—wildcards, case-insensitive rules, or predicates like vowel matches consonant. Model allowed pairs explicitly instead of ad-hoc branches.

Why this shows up in the real world

Fuzzy SKU matchers allow ? for unknown characters. Password rules check patterns with mixed constraints per position.

Core idea (explained for students)

Write match(a, b) -> bool encapsulating rules, then scan both strings with two pointers or nested alignment checks. For *-style glob patterns, recursion or DP on segments is common.

Try this in Python

def matches_wild(s: str, p: str) -> bool:
    # single ? wildcard same length only (illustrative)
    if len(s) != len(p):
        return False
    return all(pc == "?" or sc == pc for sc, pc in zip(s, p))


print(matches_wild("ab1", "a?1"))

Common mistakes

• Greedy * matching can be wrong—classic regex lesson.
• Mixing == with casefold forgetting to normalize both sides.

Key takeaways

• Encode rules in one table or function so tests stay readable.
• Start with brute force on small alphabets before optimizing.