A high-performance word indexing and search engine built in C — powered by Hash Tables and Linked Lists.

Inverted Search is a Data Structures project developed in C that efficiently indexes and searches words across multiple text files.

The project implements an Inverted Index using Hashing and Linked Lists to provide:

• ⚡ Fast word lookup
• 📊 Word occurrence tracking
• 📁 Multi-file search support

• C Programming
• Hash Tables
• Linked Lists
• Dynamic Memory Allocation
• File Handling

The database uses a hash table of size 27:

Stores the word, file count, and links to sub-nodes.

typedef struct Main
{
    char word[25];
    int file_count;
    S_node *sub_link;
    struct Main *main_link;
} M_node;

Stores the filename and word frequency for a specific file.

typedef struct Sub
{
    int word_count;
    char filename[20];
    struct Sub *sub_link;
} S_node;

📄 Input Files
      │
      ▼
✅ Validate Files
      │
      ▼
🗄️ Create Database
      │
      ▼
#️⃣ Hash Table Generation
      │
      ▼
🔠 Word Indexing
      │
      ▼
🔎 Search / 🖥️ Display / 💾 Save / 🔄 Update

╔══════════════════════════╗
║     INVERTED SEARCH      ║
╠══════════════════════════╣
║  1. Create Database      ║
║  2. Display Database     ║
║  3. Save Database        ║
║  4. Search               ║
║  5. Update Database      ║
║  6. Load Database        ║
║  7. Exit                 ║
╚══════════════════════════╝

• Reads words from one or more input text files
• Calculates hash index based on the first character of each word
• Creates Main Nodes (per word) and Sub Nodes (per file)
• Tracks word frequency per file

• Computes the hash index for the search term
• Traverses the corresponding linked list chain
• Displays:
  • Number of files containing the word
  • Frequency of the word in each file

• Accepts new text files to index
• Validates for duplicate files
• Merges new data into the existing database seamlessly

Persists the full database to a text file using a structured delimiter format:

#0;apple;2;file1.txt;3;file2.txt;5;#

Parses a saved backup file and fully reconstructs the in-memory database.

gcc *.c -o inverted_search

./inverted_search file1.txt file2.txt file3.txt

Enter word to search : embedded

✔ Word 'embedded' is present in 2 files
   📄 file1.txt  →  4 times
   📄 file3.txt  →  2 times

Working on this project provided hands-on experience with:

• 🔢 Hash Table implementation from scratch
• 🔗 Singly Linked Lists (Main & Sub node chaining)
• 📁 File I/O and database persistence
• 🧠 Dynamic memory allocation (malloc, free)
• 🗃️ Data indexing and retrieval techniques
• ⚡ Search optimization using hashing
• 🧩 Modular programming in C

• 🔡 Case-insensitive searching
• 💬 Phrase / multi-word search
• 🃏 Wildcard search support (*, ?)
• 🖼️ GUI-based interface
• 📦 Performance optimization for large datasets
• 🌐 Web-based frontend for search queries

Avinash Patil

Made with ❤️ and C