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Node Memory Structure

The Node's Blueprint

In the last section, we talked about trees using concepts like nodes and edges. Now, let's translate that idea into something a computer can understand. We need a blueprint to create our nodes. In C++, we can use a struct for this. Think of a struct as a custom data container, like a contact card. A contact card has specific fields: a name, a phone number, and an address. Our node blueprint will also have specific fields.

For a binary tree, each node needs to hold three pieces of information:

  1. The actual data it stores (like the number 10, or 55).
  2. A connection to its left child.
  3. A connection to its right child.

Here’s how we define that blueprint in C++ code.

struct Node {
    int data;     // The value stored in the node
    Node* left;   // A pointer to the left child node
    Node* right;  // A pointer to the right child node
};

Let's break that down. The int data; line is simple enough; it creates a spot to hold an integer. The other two lines, Node* left; and Node* right;, are the interesting part. The asterisk (*) tells C++ that these are not regular variables. They are pointers

pointer

noun

A variable that stores the memory address of another variable. Instead of holding a value itself, it holds the location where a value can be found.

A pointer is like writing down the address of a friend's house on a piece of paper. The paper itself isn't the house, but it tells you exactly where to find it. In our Node struct, left and right are pointers that will store the memory addresses of the left and right child nodes.

Connecting the Nodes

Notice that the type of our pointers is Node*. This means they are designed to point specifically to other Node objects. This is a powerful idea called a self-referential structure, where a structure's definition includes pointers to itself. It's how we create the links, or edges, between the parent and child nodes that form the tree.

When a new node is created, its left and right pointers don't point to anything valid yet. We typically initialize them to a special value called nullptr (or NULL), which is like a blank address. It's a placeholder that says, "This pointer doesn't lead anywhere."

A node with nullptr for both its left and right children is what we previously called a leaf node. It's a dead end in the tree.

The Node struct is the fundamental building block. Every tree, no matter how large or complex, is just a collection of these simple Node objects linked together by pointers.

With this blueprint, we can now create individual nodes. The next step will be to learn how to allocate memory for these nodes and link them together to build our first tree.