Sudoku Solver with GUI and Game Mode

A comprehensive C-based Sudoku application with a graphical user interface featuring both a powerful puzzle solver and an interactive game mode. This dual-function application allows users to solve existing puzzles or play new randomly generated ones with hints and solution checking.

Features

Solver Tab

• Interactive GUI: Easy-to-use 9x9 grid for inputting puzzles
• Fast Solving: Uses backtracking algorithm for quick solutions
• Input Validation: Only accepts valid numbers (1-9) and checks for duplicates
• Visual Feedback: Clear separation of 3x3 blocks
• Example Puzzles: Load sample puzzles to test the solver

Game Tab

• Puzzle Generation: Create random, solvable Sudoku puzzles
• Solution Checking: Verify if your completed puzzle is correct
• Hint System: Get up to 3 hints per puzzle to help you solve
• Difficulty Levels: Medium difficulty puzzles with proper number of clues

Game Mode Features

The Game tab provides an interactive Sudoku experience:

Puzzle Generation

• Automatic generation of valid Sudoku puzzles with unique solutions
• Each puzzle is guaranteed to be solvable using logic (no guessing required)
• Three difficulty levels (easy, medium, hard) with different numbers of clues

Gameplay Features

• Real-time input validation prevents obvious mistakes
• Built-in hint system (limited to 3 hints per puzzle)
• Solution checking compares your answer with the known solution
• Clear visual feedback on correct/incorrect solutions

Implementation Details

• Puzzle generation uses a diagonal-first approach for efficiency
• Difficulty is controlled by the number of clues removed
• The hint system strategically reveals cells to guide players
• All puzzles have exactly one solution to ensure fairness

How to Build

Prerequisites

• GCC compiler (MinGW recommended for Windows)
• Windows operating system

Installation

If you are on Windows and do not have make installed:

• You can use the provided PowerShell script:

  .\build.ps1

• Or, compile directly with GCC:

  gcc -Wall -Wextra -std=c99 -O2 -o sudoku_solver.exe src/main.c src/sudoku.c src/gui.c -lgdi32 -luser32 -lkernel32 -lcomctl32

If you have make installed (Linux/macOS or Windows with MinGW/MSYS2):

• Compile the project:

  make

• Or for quick build:

  make quick

How to Use

Solver Tab

1. Run the program: Double-click sudoku_solver.exe or run make run
2. Enter puzzle: Click on cells and enter numbers 1-9 in the Solver tab
3. Solve: Click "Solve Puzzle" button to find the solution
4. Clear: Use "Clear Grid" to start over
5. Load Example: Click "Load Example" to try a sample puzzle

Game Tab

1. Generate Puzzle: Click "Generate Puzzle" to create a new random puzzle
2. Play: Fill in the empty cells with numbers 1-9
3. Check Solution: Click "Check Solution" when you think you've solved it
4. Get Hints: Use "Get Hint" button (3 hints available per puzzle)
5. Switch Tabs: Click between "Solver" and "Game" tabs at the top

Example Puzzle

Try entering this puzzle:

5 3 _ | _ 7 _ | _ _ _
6 _ _ | 1 9 5 | _ _ _
_ 9 8 | _ _ _ | _ 6 _
------+-------+------
8 _ _ | _ 6 _ | _ _ 3
4 _ _ | 8 _ 3 | _ _ 1
7 _ _ | _ 2 _ | _ _ 6
------+-------+------
_ 6 _ | _ _ _ | 2 8 _
_ _ _ | 4 1 9 | _ _ 5
_ _ _ | _ 8 _ | _ 7 9

Algorithms

Solver Algorithm

Uses backtracking algorithm:

1. Find empty cell
2. Try numbers 1-9
3. Check if placement is valid (row, column, 3x3 box)
4. If valid, recursively solve rest
5. If no solution, backtrack and try next number

Puzzle Generation Algorithm

The Game tab uses an advanced puzzle generation approach:

1. Fill diagonal 3x3 boxes first (these don't affect each other)
2. Solve the rest of the grid using the solver algorithm
3. Remove numbers strategically to create a puzzle with a unique solution
4. Different difficulty levels remove different numbers of clues

Project Structure

sudoku_solver/
├── src/
│   ├── main.c     # Entry point and window creation
│   ├── sudoku.c   # Solving and puzzle generation algorithms
│   ├── sudoku.h   # Sudoku function declarations
│   ├── gui.c      # GUI implementation (solver & game tabs)
│   └── gui.h      # GUI function declarations & constants
├── Makefile       # Build configuration
├── build.ps1      # PowerShell build script for Windows
└── README.md      # This file

Technical Details

• Language: C (C99 standard)
• GUI: Windows API (native) with Common Controls
• Solver Algorithm: Backtracking with constraint checking
• Generation Algorithm: Diagonal-first with unique solution guarantee
• Tab Interface: Windows Common Controls Tab Control
• Time Complexity: O(9^n) worst case, typically much faster
• Space Complexity: O(1) excluding recursion stack
• Hint System: Limited hints (3 per puzzle) based on known solution

Screenshots

Solver Tab

The Solver tab allows you to input and solve any valid Sudoku puzzle:

Game Tab

The Game tab lets you play randomly generated puzzles:

Contributing

Feel free to submit issues and enhancement requests! Some ideas for future improvements:

• Additional difficulty levels in Game mode
• Puzzle saving/loading functionality
• Timer for gameplay
• Score tracking and statistics
• Support for additional operating systems

License

This project is open source. Feel free to use and modify as needed.