C++ Fundamentals: const with Pointers, and map vs unordered_map

This question assesses fundamental C++ knowledge, specifically focusing on const correctness with pointers and the trade-offs between std::map and std::unordered_map.

Part 1: const Pointers

Explain the difference between the following two C++ pointer declarations:

1. const int*
2. int* const

For each declaration, precisely state what is immutable, what operations are still permitted, and provide short code snippets demonstrating which assignments are valid and which are not. Additionally, explain the general rule for reading such declarations, including the case of const int* const.

Part 2: std::map vs std::unordered_map

Explain the fundamental differences between std::map and std::unordered_map.

Your explanation should cover:

• The underlying data structures used by each.
• The asymptotic complexity of core operations (insertion, deletion, lookup).
• Ordering guarantees (or lack thereof).
• The requirements placed on the key type for each container.
• Guidance on when to choose one container over the other in practical scenarios.

Constraints & Assumptions

• Assume standard C++ (C++11 or later).
• Answers should be based on typical implementations of the C++ Standard Library (e.g., libstdc++, libc++).
• The interviewer is looking for precise technical details and well-reasoned trade-offs, not just superficial answers.