What are the differences between std::map and std::unordered_map in C++11?

Can you explain the differences between std::map and std::unordered_map in C++11?

Sure! std::map is an ordered associative container that stores elements in a key-value pair, sorted by keys. std::unordered_map, on the other hand, is an unordered associative container that uses a hash table for storage, providing faster access on average.

What are the performance implications of using one over the other?

std::map has O(log n) complexity for insertions, deletions, and lookups due to its underlying balanced tree structure. std::unordered_map offers average O(1) complexity for these operations, but can degrade to O(n) in the worst case due to hash collisions.

Are there any specific use cases where one is preferred over the other?

Yes! Use std::map when you need ordered data or to perform range queries. Use std::unordered_map when you need faster access and don't care about the order of elements.

Can you give an example of how to use both in code?

Certainly! Here's a simple example:

#include <map>
#include <unordered_map>

std::map<int, std::string> orderedMap;
std::unordered_map<int, std::string> unorderedMap;

orderedMap[1] = "one";
unorderedMap[1] = "one";

This code initializes both types of maps and adds an element to each.