Recall & Review
beginner
What is a Trie data structure?
A Trie is a tree-like data structure used to store a dynamic set of strings, where each node represents a character. It allows fast retrieval of words by prefix.
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intermediate
How does a Trie help find the longest word in a dictionary where all prefixes are also words?
By inserting all words into the Trie, we can traverse nodes only if they mark the end of a word, ensuring all prefixes exist. The longest path following this rule gives the longest valid word.
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beginner
In the context of the longest word problem, why do we only continue traversal if the current node marks the end of a word?
Because the problem requires that all prefixes of the word must be valid words. If a node is not an end of a word, it means the prefix is missing, so we stop.
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intermediate
What is the time complexity of building a Trie for n words with average length m?
The time complexity is O(n * m), since each character of every word is inserted once into the Trie.
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beginner
How do you compare two candidate longest words when their lengths are equal in this problem?
You choose the lexicographically smaller word (alphabetically first) as the answer.
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What does each node in a Trie represent?
✗ Incorrect
Each node in a Trie represents a single character of a word.
Why do we only continue traversal in the Trie if the node marks the end of a word?
✗ Incorrect
Continuing only at nodes marking word ends ensures all prefixes exist as words.
What is the main goal when finding the longest word in the dictionary using a Trie?
✗ Incorrect
The problem is to find the longest word such that every prefix is also a valid word.
If two words have the same length, which one is chosen as the answer?
✗ Incorrect
The lexicographically smaller word is chosen when lengths are equal.
What is the time complexity to insert all words into a Trie?
✗ Incorrect
Inserting n words each of average length m takes O(n * m) time.
Explain how a Trie can be used to find the longest word in a dictionary where all prefixes are also words.
Think about how prefixes relate to nodes marking word ends.
You got /4 concepts.
Describe the traversal strategy in the Trie to find the longest word with all prefixes present.
Focus on conditions to continue traversal.
You got /4 concepts.