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What this C++23 std::mdspan question tests

This is a medium-difficulty question on modern C++ standard library features, specifically the multidimensional span abstraction introduced in C++23. It assesses whether you understand how std::mdspan maps logical multidimensional indices to a flat underlying buffer, and how layout policies govern that mapping.

To reason through problems like this, you need to grasp the relationship between the declared extents (shape), the layout order (row-major, column-major, or custom), and the resulting element access patterns. The question rewards careful attention to how indices are flattened and what the default layout assumption is in the standard library.

• Multidimensional indexing and strides
• Layout policies and storage order
• Span semantics and non-owning views