MEDIUM NC#61 Blind #71 Tries - Prefix Tree
208. Implement Trie (Prefix Tree)
📖 Problem
Implement a Trie with insert, search, and startsWith methods. - insert(word): Inserts word into trie - search(word): Returns true if word is in trie - startsWith(prefix): Returns true if any word with this prefix exists
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
💡 Approach
- → Trie nodes have children Map and isEndOfWord flag
- → insert: traverse/create nodes for each character, mark last as end
- → search: traverse nodes, return isEndOfWord at the end
- → startsWith: traverse nodes, return true if all characters found
- → Time: O(L) per operation where L = word/prefix length
- → Space: O(total characters inserted)
🛠️ Hints & Pitfalls
Hints
- •Trie nodes have children Map and isEndOfWord flag
- •insert: traverse/create nodes for each character, mark last as end
- •search: traverse nodes, return isEndOfWord at the end
Common Pitfalls
- •startsWith: traverse nodes, return true if all characters found
- •Time: O(L) per operation where L = word/prefix length
- •Space: O(total characters inserted)
🧪 Test Cases
Hidden tests on submit: 3
Test Case 1
Not run Input:
(() => { const trie = new Trie(); return trie.insert('apple'); })(); Expected:
null Test Case 2
Not run Input:
(() => { const trie = new Trie(); trie.insert('apple'); return trie.search('apple'); })(); Expected:
true Test Case 3
Not run Input:
(() => { const trie = new Trie(); trie.insert('apple'); trie.search('apple'); return trie.search('app'); })(); Expected:
false 📝 Code Editor
📤 Output