Longest Word in Dictionary Using Trie in DSA C++ - Cheat Sheet & Quick Revision

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 keys are usually strings. Each node represents a character, and paths from root to nodes represent prefixes of words.

intermediate

How does a Trie help in finding the longest word in a dictionary where all prefixes are also words?

A Trie allows efficient prefix checking by storing all words. We can traverse the Trie only through nodes that mark the end of a word, ensuring all prefixes exist, and track the longest such word.

beginner

In the context of the longest word problem, what does it mean if a Trie node's 'endOfWord' flag is true?

It means the path from the root to this node forms a valid word in the dictionary, which is important to ensure all prefixes exist when searching for the longest word.

intermediate

Why do we prefer Depth-First Search (DFS) on Trie nodes with 'endOfWord' true when finding the longest word?

DFS helps explore all possible words formed by valid prefixes. By only moving through nodes marking word ends, we ensure prefixes exist and can find the longest valid word.

advanced

What is the time complexity of inserting all words into a Trie and then finding the longest word with all prefixes present?

Inserting all words takes O(N * L) where N is number of words and L is average length. DFS traversal to find longest word also takes O(N * L) in worst case.

What does each node in a Trie typically represent?

A A character of a word

B A whole word

C A number

D A sentence

Each node in a Trie represents a single character of a word.

When searching for the longest word with all prefixes present, which nodes should we only traverse?

A Nodes with endOfWord true

B Nodes with no children

C Nodes with only one child

D All nodes

We only traverse nodes where endOfWord is true to ensure all prefixes are valid words.

What traversal method is commonly used to find the longest word in a Trie?

A Breadth-First Search (BFS)

B Depth-First Search (DFS)

C Level Order Traversal

D Inorder Traversal

DFS is used to explore all valid paths deeply to find the longest word.

What is the main advantage of using a Trie for prefix-related problems?

A Sorting words alphabetically

B Reducing memory usage

C Efficient prefix checking

D Faster integer calculations

Trie allows quick and efficient checking of prefixes.

If a word is 'apple', which nodes must have endOfWord true to consider it valid for the longest word problem?

A 'a' and 'apple' only

B 'apple' only

C 'appl' and 'apple' only

D 'a', 'ap', 'app', 'appl', 'apple'

All prefixes including 'a', 'ap', 'app', 'appl', and 'apple' must be valid words.

Explain how a Trie can be used to find the longest word in a dictionary where every prefix of the word is also a valid word.

Think about how prefixes relate to paths in the Trie.

Describe the steps to insert words into a Trie and then find the longest word with all prefixes present.

Focus on insertion and traversal rules.