What is the usage of unordered_map in C++?

Can you explain what unordered_map is in C++?

Sure! An unordered_map is a part of the C++ Standard Library that stores key-value pairs. It allows for fast retrieval of values based on their keys.

How does it differ from a regular map?

The main difference is that unordered_map uses a hash table for storage, which provides average constant time complexity for lookups, while a regular map is typically implemented as a balanced tree, offering logarithmic time complexity.

Can you give me an example of how to use unordered_map?

Of course! Here's a simple example:

#include <iostream>
#include <unordered_map>

int main() {
    std::unordered_map<std::string, int> ageMap;
    ageMap["Alice"] = 30;
    ageMap["Bob"] = 25;

    std::cout << "Alice's age: " << ageMap["Alice"] << std::endl;
    return 0;
}

What are some common use cases for unordered_map?

Common use cases include counting occurrences of elements, implementing caches, and storing unique items with associated values.