When should I use unordered_map in C++11?

What is unordered_map in C++11?

unordered_map is a hash table-based container that stores key-value pairs with average constant time complexity for lookups.

When should I use unordered_map instead of map?

Use unordered_map when you need faster access times and don't require the elements to be sorted.

Are there any downsides to using unordered_map?

Yes, unordered_map uses more memory than map and has worse performance in cases where order matters.

Can you give an example of using unordered_map?

Sure! Here's a simple example:

#include <unordered_map>
#include <iostream>

int main() {
    std::unordered_map<std::string, int> umap;
    umap["apple"] = 1;
    umap["banana"] = 2;
    std::cout << umap["apple"]; // Outputs 1
}