I got the basic greedy scan working without too much trouble.
Start by clarifying the problem constraints (e.g., token lengths, dictionary size, text length) and then describe a greedy left-to-right scan using a trie for efficient longest-prefix matching. For the follow-up, discuss how to decouple the matching logic from the priority rule by introducing a comparator or priority function, and analyze trade-offs between different data structures.
Pro tip: Mention that a trie can be augmented with a priority value at each terminal node to handle configurable priorities without changing the core matching algorithm. Also, discuss the time complexity: O(n * L) where n is text length and L is max token length, and how a trie reduces the constant factor.
Ask about token length limits, dictionary size, text length, and whether overlapping tokens are allowed. Confirm that greedy longest-prefix matching means always taking the longest match at each position.
Describe a naive approach: at each position, try all possible token lengths from longest to shortest and check if the substring is in the dictionary. If found, emit its ID and advance; else emit the character and advance by one.
Explain how to build a trie from the dictionary to efficiently find the longest matching token starting at a given position. Traverse the trie character by character, keeping track of the last terminal node encountered.
Discuss how to modify the trie to store a priority value at each terminal node. When multiple tokens match, instead of always picking the longest, pick the one with the highest priority according to the configured rule (e.g., insertion order, score, custom comparator).
Compare approaches: trie vs. hash set with length iteration, and discuss time/space complexity. Mention edge cases like empty text, empty dictionary, tokens longer than remaining text, and overlapping matches.
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