Inverted Search Engine

Name: Udaykumar Upputuri  
Description: Developed an Inverted index Search system in C language  
Mail: udayupputuri3525@gmail.com  

📌 Project Overview

The Inverted Search project is a command-line based application written in C that creates an inverted index from multiple text files.
It maps words -> list of files -> word occurrence count, enabling fast searching similar to how search engines work.
Instead of scanning entire files during search, the program builds a structured database using Hash Table + Linked Lists, making search operations efficient.

📖 What is Inverted Search

Inverted Search (Inverted Index) is a data structure used to store:  
Word -> File(s) -> Count  
Example:  
📂 Input Files  
file1.txt → uday kumar upputuri  
file2.txt → uday done bachelors and Uday  
🔍 Word Breakdown  
file1.txt → uday, kumar, upputuri  
file2.txt → uday, done, bachelors, and, uday     

Word: uday  
→ file1.txt (1 time)  
→ file2.txt (2 times)   
File Count: 2  

Word: kumar  
→ file1.txt (1 time)  
File Count: 1  

same like for remaining words - upputuri, done, bachelors, and,  
This allows fast lookup of words across multiple files.  

💡 Why Inverted Index

Without an inverted index:
You must scan entire files every time you search
Time complexity is high

With inverted index:
Direct access using hashing
Faster search
Organized data structure

⚙️ Features

• Supports multiple input text files
• Efficient search using Hash Table
• Tracks word frequency in each file
• Displays complete database
• Save database to file (database.txt)
• Reload database using update feature
• Handles duplicate and invalid files
• Case-insensitive indexing

📂 Project Structure

Inverted_Search
├── main.c
├── inverted.h
├── inverted.c
├── create.c
├── display.c
├── search.c
├── save.c
├── update.c
└── README.md

📄 File Description

File	          Description
main.c	          Entry point, handles menu and user interaction
inverted.h	      Structure definitions, macros, function declarations
inverted.c	      Helper functions (validation, insertion, hashing)
create.c	      Creates inverted database from input files
display.c	      Displays entire database
search.c	      Searches for a word
save.c	          Saves database to file
update.c	      Loads database from saved file
README.md	      Project documentation

🧠 Data Structures Used

1️⃣ File Linked List
Stores all valid input files
F_node: filename → next file
2️⃣ Main Node (Word Level)
M_node: word, file count, subnode link, next main node link
3️⃣ Sub Node (File Level)
S_node: filecount, word_count, next subnode link
4️⃣ Hash Table
Size: 27
Index mapping: a-z → 0 to 25 and others → 26

Overall Project Workflow

1️⃣ Input Files
User provides input files via command line: ./a.out file1.txt file2.txt file3.txt

2️⃣ File Validation
Checks: File extension (.txt), File exists, File is not empty, Duplicate files
Functions used: validate_files(), check_duplicates()

3️⃣ Create Database
Read each file word by word
Generate index using first character
Insert into hash table
Cases handled:
New word → create main node
Existing word → update sub node
New file for existing word → create sub node
Function: create_database()

4️⃣ Display Database
Displays in structured format: Index | Word | File Count | File Name | Word Count
Function: display_database()

5️⃣ Search Operation
User enters a word
Hash index is calculated
Traverse main node → sub nodes
Output: Files containing word, Number of occurrences
Function: search_database()

6️⃣ Save Database
Stores database into file (database.txt)
Format: #word;file_count;file1;count;file2;count#
Function: save_database()

7️⃣ Update Database
Loads database from file and Reconstructs hash table
Function: update_database()

🔑 Hashing Logic

if alphabet:
index = tolower(word[0]) - 'a'
else:
index = 26

🔧 Important Functions

   Function	                  Purpose
validate_files()	      Check file validity
insert_last()	          Insert file into list
check_duplicates()	      Avoid duplicate files
get_index()	              Generate hash index
create_database()	      Build inverted index
display_database()	      Show database
search_database()	      Search word
save_database()	          Save to file
update_database()	      Reload database fro saved file

🧠 Applications

• Search Engines (Google, Bing)
• Document indexing systems
• Information retrieval systems
• Text analysis tools
• Digital libraries
• Log analysis systems

✅ Advantages

• Fast searching
• Efficient data organization
• Reduces repeated file scanning
• calable for large datasets
• Demonstrates hashing + linked list concepts

❌ Disadvantages

• More memory usage
• Initial database creation takes time
• Complex implementation
• Not ideal for very small datasets
  -----------------------------------------> Thank you <--------------------------------------------