After the Erase

Understanding C++ container behavior after element erasure

This is a medium-difficulty code-reading question that tests your grasp of how C++ standard-library containers handle iterator validity and state changes following an erase operation. Questions of this type commonly appear in technical interviews to verify that candidates understand the often-subtle semantics of the Standard Template Library.

To solve it, you need to trace through the code carefully, paying attention to which iterators remain valid after erasure, what the container's contents and size are at each step, and how any subsequent operations behave given that modified state. The question rewards precision in understanding the contract between container methods—not guessing or relying on intuition.

• Iterator invalidation rules for different container types
• Container state and size after mutation
• Boundary conditions and off-by-one reasoning