📄 PDF Search Engine

A Python-based search engine for PDF documents, built as a university project for the Data Structures and Algorithms course.
The project demonstrates practical use of data structures (Trie, Stack) and algorithms (PageRank, Boolean expression parsing) in real-world search applications.

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📝 Overview

This system allows users to:

• Search for words and expressions inside PDF files
• Use Boolean operators (AND, OR, NOT)
• Get autocomplete suggestions using a * wildcard
• Rank results using a PageRank algorithm
• Receive "Did You Mean?" spelling suggestions
• Export search results to a formatted PDF

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✨ Features

Feature	Description
🔍 Fast Search	Trie data structure enables O(m) lookup (m = word length)
📊 Smart Ranking	PageRank determines relevance of PDF pages
🧠 Boolean Search	Supports AND, OR, NOT, and parentheses
🔤 Autocomplete	Use algo* to list possible word completions
🤖 Spell Suggestions	Automatic “Did you mean?” correction
💾 Caching	Stores processed results for faster startup
📄 PDF Export	Save the search results into a generated PDF

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📁 Project Structure

pdf-search-engine/
├── data/                 # PDF input files
├── serialized_data/      # Cached data (auto-generated)
└── src/
    ├── main.py           # Application entry point
    ├── config.py         # Settings and constants
    ├── trie.py           # Trie implementation
    ├── pagerank.py       # PageRank algorithm
    ├── search_engine.py  # Search orchestration logic
    ├── stack_and_postfix.py # Boolean expression parser (Shunting Yard)
    └── utils.py          # Helper functions (PDF parsing, caching, etc.)

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🚀 Installation & Running

Prerequisites

• Python 3.8+
• pip package manager

Setup

git clone <repo-url>
cd pdf-search-engine

python -m venv venv
# Windows:
venv\Scripts\activate
# macOS/Linux:
source venv/bin/activate

pip install -r requirements.txt

Run the Program

python src/main.py

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🔎 Usage Examples

Query Type	Example	Meaning
Simple Search	algorithm	Find all pages containing the word
Autocomplete	algo*	List word completions starting with algo
Boolean AND	sorting AND algorithm	Pages containing both words
Boolean OR	tree OR graph	Pages containing at least one word
Boolean NOT	data NOT structure	Pages with data but not structure
Grouping	(tree OR graph) AND algorithm	Complex prioritized queries

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⚙️ How It Works

1. PDF Parsing — Extracts text using PyMuPDF
2. Trie Construction — Stores words for fast prefix-based searching
3. PageRank Processing — Assigns relevance based on cross-page references
4. Boolean Logic Evaluation — Uses the Shunting Yard algorithm to parse expressions
5. Output Formatting — Displays ranked results and allows PDF export

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🧠 Data Structures & Algorithms

Component	Purpose
Trie	Efficient word lookup and autocomplete
Stack	Parsing and evaluating Boolean expressions
Graph + PageRank	Ranking relevance of pages
Shunting Yard Algorithm	Converting infix to postfix expressions

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🚧 Future Improvements

• Support multiple PDF files at once
• Add full sentence / phrase search
• Use Levenshtein Distance for improved autocorrect
• Build simple web UI frontend

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🎓 Course Information

• Course: Data Structures and Algorithms
• Level: 1st Year University
• Focus: Practical application of Trie, Stack, and PageRank