Parameterized Constructor for Node Based Linked List

Question

I'm in CS2 and we're just learning about linked lists and I have to code the parameterized constructor of a linked list class (node based). I don't really understand the node lists, so any help of what's going on here or how to approach would be helpful! I have the following Node class given:

class Node {

friend class NodeList;

public:
 Node() : m_next(NULL) {}
 Node(const DataType& data, Node* next = NULL) :
        m_next(next), m_data(data) {}
 Node(const Node& other) : m_next(other.m_next),
                           m_data(other.m_data) {}

 DataType& data() { return m_data; }

 const DataType& data() const { return m_data; }

private:
 Node* m_next;
 DataType m_data;
};

and I'm trying to create the parameterized constructor for the following class:

Class NodeList {
    public:
     NodeList();
     NodeList(size_t count, const int value);
    private:
     Node* m_head;
}

, where the parameterized constructor is supposed to have 'count' nodes initialized to 'value'.

Thank you!

Alecto · Accepted Answer · 2019-04-19 05:25:18Z

Solving a problem like this has 3 parts.

Break the problem down into smaller, simpler tasks that make it easier to solve
Do the smaller tasks
Use them to solve the big problem.

What would make it easy to solve this problem? Adding one value to a list is easier than adding multiple values to a list, so let's write a function to do that.

To add one value at the beginning of the list,

We can create a new node with that value
We have the new node point to the current first node
We set the current first node to the new node.

Let's call our function prepend, since it prepends the value to the list.

class NodeList {
   public:
    // The head should be set to null initially
    NodeList() 
      : m_head(nullptr) 
    {
    }
    // This function takes a value and adds it to the beginning of the list
    void prepend(const DataType& value) {
        // The new node uses the current head as the next value
        Node* newNode = new Node(value, m_head); 
        // We set the current head to the new node. 
        m_head = newNode; 
    }

Now, adding a value multiple times is easy. We can just call prepend once for each time we want to add an item.

class NodeList {
   public:
    // The head should be set to null initially
    NodeList() 
      : m_head(nullptr) 
    {
    }
    // This function takes a value and adds it to the beginning of the list
    void prepend(const DataType& value) {
        // The new node uses the current head as the next value
        Node* newNode = new Node(value, m_head); 
        // We set the current head to the new node. 
        m_head = newNode; 
    }

    NodeList(size_t count, const DataType& value) 
      : m_head(nullptr) // The head still has to be null initially
    {
        for(size_t i = 0; i < count; i++) 
        {
           prepend(value); 
        }
    }
};

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