How do I merge two containers efficiently with std::deque in performance-sensitive code?

Merging two std::deque containers efficiently is a common requirement in performance-sensitive C++ applications. By following a few best practices, you can ensure that the merge operation utilizes the optimal time complexity and memory efficiency.

The most efficient way to merge two std::deque objects is to use the insert member function, which allows you to insert the entire range of one deque into another without copying individual elements.

#include <iostream>
#include <deque>

int main() {
    std::deque<int> deque1 = {1, 2, 3, 4, 5};
    std::deque<int> deque2 = {6, 7, 8, 9, 10};

    // Merging deque2 into deque1
    deque1.insert(deque1.end(), deque2.begin(), deque2.end());

    // Display the merged deque
    for (const auto& num : deque1) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}
    

This method is efficient because it minimizes the need for copying elements multiple times. The insert function constructs the necessary space in the target deque only once, thus improving performance.