How do I provide stable iteration order with std::unordered_map for embedded targets?

When working with embedded targets, providing a stable iteration order with std::unordered_map can be challenging due to its nature of being an unordered container. However, you can achieve this by using a combination of other data structures to maintain the order in which elements are inserted. Below is an example of how to implement this using a vector alongside the unordered map.


    #include <iostream>
    #include <unordered_map>
    #include <vector>

    class StableOrderedMap {
    public:
        void insert(int key, int value) {
            if (map.find(key) == map.end()) {
                order.push_back(key); // Maintain insertion order
            }
            map[key] = value;
        }

        void display() {
            for (int key : order) {
                std::cout << key << ": " << map[key] << std::endl;
            }
        }

    private:
        std::unordered_map<int, int> map;
        std::vector<int> order;
    };

    int main() {
        StableOrderedMap som;
        som.insert(2, 40);
        som.insert(1, 20);
        som.insert(3, 30);

        som.display(); // Output will respect insertion order
        return 0;
    }

How do I provide stable iteration order with std::unordered_map for embedded targets?

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How do I provide stable iteration order with std::unordered_map for embedded targets?

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