Fix sudoku exercise answer checking and variable naming conflicts in optimization_basics.jl

[Copilot]

This PR fixes critical issues in the optimization exercises in class01/background_materials/optimization_basics.jl that were preventing proper functionality in Pluto.jl notebooks.

Issues Fixed

1. Sudoku Exercise Answer Checking (Issue #32)

Tuple Syntax Error: The ground_truth_s definition was missing a trailing comma, causing it to create a Vector instead of a NamedTuple:

# Before (creates a Vector)
ground_truth_s = (x_ss = [[matrix]])

# After (creates a proper NamedTuple)  
ground_truth_s = (x_ss = [[matrix]],)

Incompatible Matrix Format Comparison: The answer checking was attempting to directly compare incompatible matrix formats:

• anss.x_ss: A 3D binary matrix from JuMP.value.(sudoku[:x_s]) where x_s[i,j,k] = 1 means value k is at position (i,j)
• ground_truth_s.x_ss: A 2D solution matrix with sudoku values 1-9

Solution: Added a conversion function convert_3d_to_solution() that transforms the 3D binary indicator matrix into the standard 2D sudoku solution format for proper comparison.

2. Variable Naming Conflicts (Issue #31)

Fixed a Pluto.jl variable naming conflict in the Rosenbrock valley exercise where line 726 incorrectly referenced a bare x variable:

# Before (causes Pluto.jl conflict)
elseif x == 25.0

# After (correctly references student answer)
elseif ansd == 25.0

This was causing conflicts because x referenced the JuMP variable from the NLP model instead of the student's answer ansd, creating variable dependency issues in Pluto.jl.

Verification

• Both fixes maintain backward compatibility
• File parses successfully without syntax errors
• No other variable naming conflicts identified
• Changes are minimal and surgical

Fixes #32 and #31.

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[klamike]

Did you trigger this somehow @andrewrosemberg ? Or it will just randomly create its own bug fix PRs?

[andrewrosemberg]

Did you trigger this somehow @andrewrosemberg ? Or it will just randomly create its own bug fix PRs?

trigger in the issue

[andrewrosemberg]

@copilot can you also propose a fix for #31 in this PR!

[Copilot]

@copilot can you also propose a fix for #31 in this PR!

I've added the fix for issue #31 to this PR! The problem was a variable naming conflict in line 726 where x == 25.0 should have been ansd == 25.0. This was causing Pluto.jl conflicts by referencing a bare x variable instead of the student's answer. Fixed in commit 4784231.

[andrewrosemberg]

@ivanightingale might checking if these solved your problem? It seems that it now works for me