How can a bidirectional linked list be transformed into a format suitable for storage or transmission?

To convert a doubly linked list into a format suitable for storage or transmission (for example, to a file or over a network), it is usually serialized into a data sequence that preserves the structure and node values.

Main approaches:

• Linear serialization — traverse the list from head to tail and record the node values into an array or stream. During reconstruction, the list can be recreated by setting pointers.
• Serialization with indices — if it is necessary to preserve the connections between nodes, for each node, record its value and the indices of the previous and next nodes.

Example of simple serialization in C++:

struct Node {
    int data;
    Node* prev;
    Node* next;
};

// Serialization: write values to a file
void serialize(Node* head, std::ostream& out) {
    Node* current = head;
    while (current) {
        out << current->data << " ";
        current = current->next;
    }
}

// Deserialization: read values and create list
Node* deserialize(std::istream& in) {
    Node* head = nullptr;
    Node* tail = nullptr;
    int value;
    while (in >> value) {
        Node* newNode = new Node{value, tail, nullptr};
        if (!head) head = newNode;
        if (tail) tail->next = newNode;
        tail = newNode;
    }
    return head;
}

Thus, the doubly linked list is transformed into a linear data stream that is easy to store and transmit.