How do I sort and stable_sort elements with std::multimap?

In C++, you can use a `std::multimap` to store key-value pairs where multiple values can be associated with the same key. However, `std::multimap` automatically keeps its elements sorted based on the keys, and there is no direct method for stable sorting as you would find in vectors or lists. Instead, you can achieve stable sorting by copying the elements into a vector, sorting that vector, and then inserting the sorted elements back into the multimap if needed.

C++, std::multimap, sorting, stable_sort, key-value pairs

A demonstration of sorting and stable sorting elements in std::multimap in C++.


        #include <iostream>
        #include <map>
        #include <vector>
        #include <algorithm>

        int main() {
            // Create a multimap
            std::multimap mmap;
            mmap.insert({1, "apple"});
            mmap.insert({2, "banana"});
            mmap.insert({1, "avocado"});
            mmap.insert({3, "cherry"});
            mmap.insert({2, "blueberry"});

            // Copy to a vector to perform stable sort
            std::vector<:pair std::string>> vec(mmap.begin(), mmap.end());

            std::stable_sort(vec.begin(), vec.end(), [](const auto &a, const auto &b) {
                return a.second < b.second; // Sort by value
            });

            // Clear multimap and insert sorted elements
            mmap.clear();
            for (const auto &pair : vec) {
                mmap.insert(pair);
            }

            // Output sorted multimap
            for (const auto &pair : mmap) {
                std::cout << pair.first << ": " << pair.second << std::endl;
            }

            return 0;
        }

C++ std::multimap sorting stable_sort key-value pairs

How do I sort and stable_sort elements with std::multimap?

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How do I sort and stable_sort elements with std::multimap?

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