Trie-based Autocomplete

Trie for inserting words and suggesting completions for a prefix

Problem Overview

🔍 The Search Optimization Champion
The Trie (prefix tree) is a specialized tree data structure that revolutionizes text searching and autocomplete functionality! Store thousands of words efficiently and provide instant prefix-based suggestions.

🧠 The Tree Strategy:

Prefix Sharing: Common prefixes share the same path from root
Character Nodes: Each node represents a character, edges form words
Word Boundaries: Special markers indicate complete words vs partial paths
Traversal Magic: DFS from prefix node finds all possible completions
Two Implementation Approaches:
Map-Based: Flexible storage for any character set (Unicode support)
Array-Based: Optimized for lowercase a-z with direct indexing
Real-World Applications:
Search Engines: Autocomplete suggestions and spell checking
Code Editors: Variable/function name completion and IntelliSense
Mobile Keyboards: Predictive text and word suggestions
DNS Resolution: Efficient domain name lookup and routing
IP Routing: Network packet routing through prefix matching
Lexical Analysis: Tokenization in compilers and parsers

💡 Learning Value:

Tree-based data structure design and traversal
Space vs time optimization trade-offs
Depth-first search algorithms and recursion
Prefix matching and string processing algorithms

Concepts

tree data structuresDFS traversal

Complexity Analysis

Time:O(k) insert/suggest

Space:O(total chars)

Performance Notes:

- Time: O(k) for insert/search (k = word length, independent of dictionary size!) - Space: O(total characters across all words)

Solutions

Trie

Time: O(k) | Space: O(total chars)

Examples & Test Cases

#1Suggestions for 'ap' prefix

Input:

{
  "operations": [
    [
      "insert",
      "apple"
    ],
    [
      "insert",
      "app"
    ],
    [
      "insert",
      "application"
    ],
    [
      "suggest",
      "ap"
    ]
  ]
}

Output:

[
  "app",
  "apple",
  "application"
]

#2No suggestions for unmatched prefix

Input:

{
  "operations": [
    [
      "insert",
      "hello"
    ],
    [
      "suggest",
      "world"
    ]
  ]
}

Output:[]

#3Empty prefix

Input:

{
  "operations": [
    [
      "suggest",
      ""
    ]
  ]
}

Output:[]

#4Empty word and prefix

Input:

{
  "operations": [
    [
      "insert",
      ""
    ],
    [
      "suggest",
      ""
    ]
  ]
}

Output:

[
  ""
]