🔍 Inverted Search Project (C)

📘 Overview

The Inverted Search Project is a C-based text indexing and searching program that demonstrates the core principles of how search engines organize and retrieve information.

It uses hash tables and linked lists to build an inverted index — a data structure that maps words to the files they appear in, enabling efficient and fast word-based search operations across multiple text files.

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🧑‍💻 Author

Name: Pankaj Kumar
Roll No: 25008_018
Date: 14-Sep-2025

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⚙️ Features

• ✅ Command-line file validation: Accepts multiple .txt files as input.
• 🗂️ Dynamic Database Creation: Builds a word-to-file mapping using a hash table.
• 🧾 Display Database: Prints all words with their corresponding file occurrences.
• 🔎 Search Functionality: Quickly searches for a word across all indexed files.
• 💾 Save Database: Saves the generated index to a backup file for future use.
• 🔁 Update Database: Adds new files to an existing database (without rebuilding).
• 🧩 Modular Design: All features are separated into logical modules for clarity.
• 🚫 Input Validation: Prevents invalid or duplicate database operations.

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🧱 Core Concepts & Data Structures

Component	Description
Hash Table	Used to store words efficiently based on computed hash values.
Linked List (FileList)	Stores valid filenames passed as arguments.
Structures	Define word nodes, file nodes, and hash buckets.
Flags	Used to control duplicate creation or updates of the database.

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🗂️ Project Structure

File / Folder	Description
main.c	Entry point with menu-driven interface
list.c / list.h	Manages file list using linked lists
validate.c / validate.h	Validates input files and command-line arguments
database.c / database.h	Core database creation and management logic
hash.c / hash.h	Implements hash table for word indexing
search.c	Searches a word in the inverted database
display.c	Displays the complete inverted index
save.c	Saves the database to a backup file
update.c	Updates the existing database with new files
files/	Directory containing input text files
README.md	Project documentation

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🧠 Program Flow

1. Command-Line Validation

• Program expects at least one file name as an argument.
• Example:

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

2. Menu Options

• Once started, the user interacts through a menu-driven interface: Option Description

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1	Create Database (build inverted index)
2	Display Database (view all indexed data)
3	Search Word (find word occurrence across files)
4	Save Database (store to backup file)
5	Update Database (add new files)
0	Exit program

💻 Compilation & Execution

Compile

Use GCC or any C compiler:

gcc main.c list.c validate.c database.c hash.c search.c display.c save.c update.c -o inverted_search

RUN

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

Sample Ecexution

$ ./inverted_search file1.txt file2.txt

Valid files:
file1.txt
file2.txt

===== MENU =====
1. Create Database
2. Display Database
3. Search Word
4. Save Database
5. Update Database
0. Exit
Enter choice: 1

INFO: Database created successfully!

🧾 Example Output

=============================
        INVERTED INDEX
=============================
Word       | File Count | Files
--------------------------------
data       |     2      | file1.txt, file2.txt
search     |     1      | file1.txt
engine     |     1      | file2.txt
--------------------------------

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🧰 Functions Used

Function	Description
initialize_hashTable()	Initializes the hash table with NULL values.
read_and_validate_args()	Validates and creates the list of valid input files.
create_database()	Builds the inverted index.
display_database()	Displays the complete hash table contents.
search_word()	Searches for a specific word.
save_database()	Saves the database to a file.
update_database()	Adds new files to the existing database.}

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🪄 Future Enhancements

Add case-insensitive search support.

Implement word frequency counting per file.

Integrate stop word filtering (ignore words like “the”, “is”, etc.).

Add persistent storage using binary files.

Develop a web or GUI interface for easier interaction.