The multiplication part clicked pretty fast.
Clarify that the task is to count distinct phrases, not total replacements, and that only words with at least one anagram in the word list are replaceable. Build a hash map from sorted-letter signatures to lists of anagrams, then for each phrase compute the product of (number of anagrams + 1) for each replaceable word, subtracting 1 if no word is replaceable.
Pro tip: Mention that using a canonical sorted-string key for anagrams avoids comparing every pair of words, reducing preprocessing from O(N*M*L) to O(N*L log L), and that the product formula naturally handles distinctness because anagram sets are disjoint.
Confirm that 'distinct phrases' means unique sequences of words, and that a word with no anagram match stays fixed. Ask about case sensitivity, empty lists, and whether the original phrase counts as a valid formation.
For each word in the word list, compute a canonical key (e.g., sorted characters) and group words by that key. This yields a map from key to list of anagrams.
For each word in the phrase, check if its canonical key exists in the anagram map. If yes, it is replaceable with k options (where k is the size of the anagram list); if no, it is fixed with 1 option.
Multiply the number of options for each replaceable word. If no word is replaceable, the count is 0; otherwise, the product gives the total distinct phrases (including the original).
Discuss time and space complexity: O(W * L log L) for preprocessing, O(P * L log L) for phrase processing, where W is word list size, P is phrase count, L is average word length. Mention that sorting keys is a trade-off between preprocessing time and lookup speed.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.