create a doubly linked list in C++

Question

I'm creating a programme that needs to read data from a spreadsheet in CSV form and assigns it to a doubly linked list in C++.I have created a singly linked list but I'm at a loss as to how to use this idea to make a doubly linked list. I understand you require a previous pointer but I am unsure as to actually implementing the code.

code for my singly linked list: to add to the list:

if (!m_head)
{
    m_head = new Node(name, reference,latitude,longitude);
}
else
{
    Node *current = m_head;
    while (current->getNext() != 0)
    {
        current = current->getNext();
    }
    current->setNext(new Node(name, reference,latitude,longitude));
}

please note: Node is a separate class to store data about the node e.g. name.

The class object needs one more reference, to the previous node. The functions of the class are what need to be modified the most, for example add needs to use a reference to hold the new previous node so that the new node's previous node reference can be assigned to it. The logic is pretty simple. — Adrian M.
– Adrian M., Commented Mar 30, 2016 at 15:46

alessalessio · Accepted Answer · 2016-03-31 09:20:32Z

2

Each List Node must a have a pointer to the previous and to the next List Node. The List is then the container of List Nodes , linked together as a chain.

struct ListNode;

typedef struct ListNode {
    struct ListNode *next;
    struct ListNode *prev;
    void *value;
} ListNode;

typedef struct List {
    int count;
    ListNode *first;
    ListNode *last;
} List;

You need then to implement the methods push and pop accordingly. The tricky part is the remove method. Store the two pointers of the previous and next Node that you want to delete, and then assign them accordingly to the previous and following node:

ListNode *after = node->next;
ListNode *before = node->prev;
after->prev = before;
before->next = after;

This article may help you, full code and explanation

http://c.learncodethehardway.org/book/ex32.html

edited Mar 31, 2016 at 9:20

answered Mar 30, 2016 at 15:47

alessalessio

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2 Comments

Dennis Over a year ago

You should not give link-only answers. Quote the most relevant part in this answer.

alessalessio Over a year ago

Done. Added most relevant part

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