DS The Node Class

Section 4.4 The `Node` Class

The basic building block for the linked list implementation is the node. Each node object must hold at least two pieces of information. First, the node must contain the list item itself. We will call this the data field of the node. In addition, each node must hold a reference to the next node. Listing 4.4.1 shows the C++ implementation. To construct a node, you need to supply the initial data value for the node. Evaluating the assignment statement below will yield a node object containing the value 93 (see Figure 4.4.2). You should note that we will typically represent a node object as shown in Figure 4.4.3. The Node class also includes the usual methods to access and modify the data and the next reference.

#include <iostream>
using namespace std;

class Node {
    private:
            int data; //data in the beginning node
            Node *next; //pointer to the next node

    public:
            Node(int initdata) {
                    data = initdata; //the initialized data is set as the head
                    next = NULL; //the next node is set as NULL, as there is no next node yet.
            }

            int getData() { //function that return data of a given node.
                    return data;
            }

            Node *getNext() {
                    return next;
            }

            void setData(int newData) {
                    data = newData;
            }

            void setNext(Node *newnext) {
                    next = newnext;
            }
};

Listing 4.4.1. Node Class

>>> temp = Node(93) //sets the nodes data to the integer 93
>>> temp.getData() // calls the getData() function.
93

The special C++ reference value NULL will play an important role in the Node class and later in the linked list itself. A reference to NULL will denote the fact that there is no next node.

Note:

in the constructor that a node is initially created with next and a pointer to NULL. Since this is sometimes referred to as “grounding the node,” we will use the standard ground symbol to denote a reference that is referring to NULL.

Figure 4.4.2. A Node Object Contains the Item and a Reference to the Next Node

Figure 4.4.3. A Typical Representation for a Node

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Section 4.4 The Node Class

Section 4.4 The `Node` Class