What are some advanced techniques for using maps and unordered maps in C++?

What are some advanced techniques for using maps and unordered maps in C++?

In C++, maps and unordered maps are powerful data structures. Advanced techniques include using custom comparators, leveraging emplace for efficiency, and understanding the performance implications of each.

Can you explain how custom comparators work with maps?

Sure! Custom comparators allow you to define your own sorting criteria for the keys in a map. You can create a struct or a function that implements the comparison logic.

What is the difference in performance between map and unordered_map?

Maps are implemented as balanced trees, providing O(log n) complexity for insertions and lookups. Unordered maps use hash tables, offering average O(1) complexity, but can degrade to O(n) in worst-case scenarios.

How can I efficiently iterate over a large unordered_map?

You can use range-based for loops or iterators to traverse an unordered_map. Additionally, consider reserving space in advance to minimize rehashing during insertions.