2 variables 1 auto

What this C++ type-deduction interview question tests

This is a medium-difficulty question on C++ type deduction, specifically testing your understanding of how the auto keyword interacts with variable initialization. It is a common filter question at quant shops and trading firms where C++ expertise is non-negotiable, since incorrect type assumptions can lead to subtle bugs in high-performance code.

To solve problems like this, you need to trace through the initialization carefully, understanding how the compiler resolves types in context. This includes awareness of reference decay, const/volatile qualification, and the difference between deduction rules for template parameters versus explicit auto declarations. Interviewers use these questions to confirm that candidates have internalized the rules rather than guessing based on intuition.

• Template argument deduction rules
• Reference collapsing and decay
• Const and volatile qualification in deduction
• Interaction between initializer type and auto placeholder