Ordered Map vs Unordered Map in C++11

What are the main differences between ordered_map and unordered_map in C++11?

The main difference is that ordered_map maintains the order of elements based on their keys, while unordered_map does not.

When should I use ordered_map instead of unordered_map?

Use ordered_map when you need to maintain the order of elements or require sorted keys. Use unordered_map for faster access.

Can you give me an example of how to use both in C++?

Sure! Here's a simple example:

#include <iostream>
#include <map>
#include <unordered_map>

int main() {
    std::map<int, std::string> orderedMap;
    std::unordered_map<int, std::string> unorderedMap;

    orderedMap[1] = "one";
    orderedMap[2] = "two";

    unorderedMap[1] = "one";
    unorderedMap[2] = "two";

    // Output elements
    for (const auto& pair : orderedMap) {
        std::cout << pair.first << " : " << pair.second << '\n';
    }

    for (const auto& pair : unorderedMap) {
        std::cout << pair.first << " : " << pair.second << '\n';
    }
}

This will show the ordered output for ordered_map and a random order for unordered_map.

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

unordered_map generally offers average constant time complexity for insertions and lookups, while ordered_map has logarithmic time complexity due to its underlying tree structure. So, unordered_map is faster for most operations.