Projection-Based Sort

What this C++ language-knowledge question tests

This is a medium-difficulty question that probes your understanding of how modern C++ handles custom comparators and sorting semantics. It requires you to trace through code carefully and predict output, which is a common interview technique to assess whether you truly understand the tools you use rather than just knowing their names.

The question focuses on how projection-based sorting (or similar advanced comparison patterns) behaves in practice, and whether you can reason about the order of operations and the final state of a data structure after sorting is applied. This matters in quant environments where subtle bugs in sorting or ordering logic can corrupt portfolios or risk calculations.

• Comparator semantics and strict weak ordering
• How standard library sort functions interpret comparison results
• Tracing execution of code with custom logic