Bug/dots boxes

[yuvraj-k-singh]

📝 Description

Resolved a critical game-crashing bug caused by an IndexError during row/column selection in the Dots & Boxes AI game.

Root Cause:
While numbers that were too large threw an exception, Python natively handles negative integer indexes (e.g., -1). When a user input negative values, it altered lines on the opposite side of the grid instead of crashing immediately. Furthermore, relying entirely on a trailing try/except block allowed unchecked bounds parameters to bypass early loop sanitization.

Fix Details:

• Upgraded user input parsing to explicitly screen out negative string integers containing the - character.
• Replaced the loose try/except IndexError structure with strict, deterministic boundary validation tailored precisely to the game's asymmetric horizontal ($(size + 1) \times size$) and vertical ($size \times (size + 1)$) line matrices.
• Handled out-of-range selections smoothly by logging console alerts and retaining current turn conditions without altering board states or causing a crash.

🔗 Linked Issue

Closes #629

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📋 Contribution Checklist

• My code strictly adheres to the project guidelines (Standard library only, procedural code, clean spacing).
• I have verified that my files are placed in the correct directory.
• I have tested my changes thoroughly on my local machine.
• I have included interactive emojis and clean console/UI outputs.
• GSSoC 2026: I have been formally assigned to this issue and noted it above.

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[github-actions]

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