Question

The table below represents a linked list using the same format as in the preceding problems. If the head pointer contains the value \(0 \times 44\), what name is represented by the list? Change the pointers so that the list contains the name Jean. $$ \begin{array}{cc} \text { Address } & \text { Contents } \\ 0 \mathrm{x} 40 & ' \mathrm{~N} \text { ' } \\ 0 \mathrm{x} 41 & 0 \mathrm{x} 46 \\ 0 \mathrm{x} 42 & ' \mathrm{I} \text { ' } \\ 0 \mathrm{x} 43 & 0 \mathrm{x} 40 \\ 0 \mathrm{x} 44 & ' \mathrm{~J} \text { ' } \\ \text { 0x45 } & 0 \mathrm{0x} 4 \mathrm{~A} \\ 0 \mathrm{x} 46 & ' \mathrm{E} \text { ' } \\ \text { 0x47 } & 0 \mathrm{x} 00 \\ 0 \mathrm{x} 48 & ' \mathrm{M} \text { ' } \\ \text { 0x49 } & 0 \mathrm{0x} 42 \\ \text { 0x4A } & ' \mathrm{~A} \text { ' } \\ \text { 0x4B } & 0 \mathrm{x} 40 \end{array} $$

Short answer

The current list spells "JANE"; change pointers to order: 0x46, 0x4A, 0x40 for "JEAN".

Step-by-step solution

Understand the Linked List Structure

The linked list is represented as a series of address-value pairs where each node stores a character and a pointer to the next node. The "head" of the list is at address 0x44. Our task is to traverse the list starting from the head and identify the sequence of characters to form the name.

Traverse the Initial Linked List

Starting at the head pointer 0x44, locate the character at this address, which is 'J'. Then, follow the pointer in the next address (0x45) to know where to go next. Continue this process until you reach a termination node (0x47) which points to 0x00 indicating the end of the list.

Identify the Current Name in the List

Following the pointers from 0x44: - 0x44: 'J' - [next at 0x45]: location 0x4A - 0x4A: 'A' - [next at 0x4B]: location 0x40 - 0x40: 'N' - [next at 0x41]: location 0x46 - 0x46: 'E' - [next at 0x47]: location 0x00 (end) The current name in the list is "JANE".

Plan to Change the List to "JEAN"

To change the name to "JEAN", you need characters in this order: J (at 0x44), E (at 0x46), A (at 0x4A), and N (at 0x40). The pointers must follow this sequence to ensure the linked list is correctly ordered.

Adjust the Pointers

You need to change the pointers as follows: - At 0x45: Point to 0x46 (to link J to E) - At 0x47: Point to 0x4A (to link E to A) - At 0x4B: Point to 0x40 (to link A to N) Ensure this follows the desired sequence for "JEAN" and end the list after 'N' at 0x41 with a null pointer (0x00).

Key concepts

Linked Lists

A linked list is a basic data structure that consists of a collection of nodes. Each node contains two main components:

• A data part, which holds the actual information (like a character in this exercise).
• A reference part, typically known as a pointer, that indicates the address of the next node in the sequence.

This format allows for flexible and dynamic memory usage, making it a highly useful structure in programming.
Unlike arrays, linked lists don’t require contiguous memory blocks. This makes them ideal for scenarios where the size of the element set cannot be predetermined.
In the given exercise, each address represents a node that holds a character and a pointer, creating a sequence that forms a name.

Pointers

Pointers in linked lists play a crucial role. They help maintain the order of elements and allow the traversal from one node to the next.
Each pointer in a node points to the location of the next node, forming a chain-like structure.
Consider each node as having its own mailing address, and the pointer is simply a note that says, "Where should the mail be forwarded next?"

• The value stored in the pointer determines which node in the list will be accessed next.
• If a pointer points to a 'null' or 'zero', it indicates the end of the list.

In our exercise, adjusting the pointers is equivalent to changing addresses in our mailing sequence to ensure the name "JEAN" is correctly traversed.

Node Traversal

Traversing a linked list involves starting at the "head" node and following the pointers from one node to the next.
This process continues until a termination is found (a null pointer).
During traversal, each node's data can be accessed, allowing us to read through all elements stored in the list.

• Begin at the key address known as the head (0x44 in the exercise).
• Read the data and then check the pointer for the next node's address.
• Move to the address as indicated by the pointer and repeat the process.

This sequential method is fundamental to linked lists and is used for various operations including addition, deletion, and searching for nodes within the list. For our task, this also enabled us to follow pointers to identify the name and make necessary changes to arrange nodes as per needed.