How do I use std::unordered_map in C++17?

How do I use std::unordered_map in C++17?

In C++17, std::unordered_map is a hash table implementation that allows for fast retrieval of key-value pairs. You can include it by adding #include <unordered_map>. Would you like a code example?

Yes, please provide a code example.

Sure! Here's a simple example:

#include <iostream>
#include <unordered_map>

int main() {
    std::unordered_map<std::string, int> map;
    map["apple"] = 1;
    map["banana"] = 2;

    for (const auto& pair : map) {
        std::cout << pair.first << ": " << pair.second << std::endl;
    }
    return 0;
}

This code creates an unordered_map, adds some fruit counts, and prints them.

What are the advantages of using unordered_map over map?

The main advantage of std::unordered_map is its average constant time complexity for lookups, insertions, and deletions, compared to std::map, which has logarithmic time complexity due to its underlying tree structure. This makes unordered_map faster for large datasets where order is not important.