Wildcard Substring Index | Dataford Interview Questions

Your question is Wildcard Substring Index. Start with the requirements on the right.

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Problem

Simon AI receives event names from its product surfaces and needs to locate the first event name matching a partially specified pattern. Given a text string and a pattern containing exactly one ? wildcard, return the lowest index where the pattern matches. The wildcard matches exactly one arbitrary character.

A match must use consecutive characters in text. Return -1 if no match exists.

Formal Specification

Implement find_substring(text, pattern):

text is a string.
pattern is a non-empty string containing exactly one ?.
Every pattern character other than ? must match the corresponding text character exactly.
Return an integer start index, using zero-based indexing.

For an efficient solution, avoid checking every complete candidate substring character by character. Use string-search techniques to locate the fixed prefix and suffix around the wildcard.

Constraints

1 <= len(text) <= 10^5
2 <= len(pattern) <= 10^4
pattern contains exactly one ?
? matches exactly one character
Matching is case-sensitive

Function Signature

def find_substring(text, pattern):