Passing containers to templated utilities

Understanding template instantiation with standard containers in C++

This is a medium-difficulty C++ language-knowledge question that tests your grasp of how templates interact with the standard library. It rewards precise understanding of template argument deduction, container types, and what the compiler actually instantiates when you pass STL containers to templated utilities.

Working through this question requires you to mentally trace the template instantiation process: identify what type is deduced, reason about how that type matches (or fails to match) the template parameters, and predict whether the code compiles and what it produces at runtime. The question often hinges on subtle distinctions between container interfaces, iterator semantics, or type conversions that only emerge under scrutiny.

• Template argument deduction and type matching
• STL container type signatures and decay rules
• Compiler error messages and template substitution failure