Find substring from dictionary concatenation
Overview
This question evaluates proficiency in string-processing algorithms, word-lookup data structures and algorithmic complexity analysis within the Coding & Algorithms domain. It is commonly asked to assess practical implementation ability and conceptual understanding of performance trade-offs, edge-case handling (e.g.
Given a string s and a dictionary of words dict, determine whether s contains a substring that is exactly a concatenation of one or more words from dict (words may be reused; order is arbitrary). Return the start index of any one such substring, or -1 if none exists. Words can have varying lengths. Discuss an efficient algorithm, its time and space complexity, and edge cases (e.g., overlapping matches, very large dict, unicode). Implement a function solve(s: string, dict: List[str]) -> int.