How do I use unordered_map in C++11 effectively?

Can you explain how to use unordered_map in C++11?

Sure! unordered_map is a hash table implementation in C++11 that allows for fast retrieval of key-value pairs.

What are the advantages of using unordered_map over map?

The main advantage is performance; unordered_map offers average constant time complexity for lookups, while map has logarithmic time complexity.

Can you show me a simple example of unordered_map?

Of course! Here's a basic example:

#include <iostream>
#include <unordered_map>

int main() {
    std::unordered_map<std::string, int> umap;
    umap["apple"] = 1;
    umap["banana"] = 2;
    std::cout << "Apple: " << umap["apple"] << '\n';
    return 0;
}

Are there any specific use cases where unordered_map is preferred?

Yes, unordered_map is preferred when you need fast access to elements and don't require the elements to be sorted.