Explanation of the Code Snippet

Overview

This code snippet defines and manipulates a linked list using a Python class. The key components include node definition, linked list traversal, and node addition functionalities. The main program leverages these components to demonstrate the linked list operations.

Code Breakdown

Node Class Definition

class node:
    def __init__(self, data, nextnodedata):
        self.Data = data
        self.nextNode = nextnodedata

1. __init__ Method: This constructor initializes a node object with data and nextNode.
   • self.Data: Stores the value of the node.
   • self.nextNode: Stores the pointer to the next node in the linked list.

Output Function

def outputNodes(linkedList, currentPointer):
    while currentPointer != -1:
        print(linkedList[currentPointer].Data)
        currentPointer = linkedList[currentPointer].nextNode

1. outputNodes Function: Traverses and prints the data in each node sequentially.
   • Parameters:
     • linkedList: The list containing nodes.
     • currentPointer: The starting pointer of the linked list.
   • The loop continues until currentPointer is -1 (indicating the end of the list).

Add Node Function

def addNode(linkedList, currentPointer, emptyList):
    newData = int(input("Enter new data: "))
    
    if (emptyList < 0) or (emptyList > 9):
        return False
    else:        
        newNode = node(newData, -1)
        linkedList[emptyList] = newNode
        
        previousPointer = 0
        while(currentPointer != -1):
            previousPointer = currentPointer
            currentPointer = linkedList[currentPointer].nextNode
        linkedList[previousPointer].nextNode = emptyList
        emptyList = linkedList[emptyList].nextNode
        return True

1. addNode Function: Adds a new node to the linked list.
   • Prompts the user for new node data.
   • Checks if emptyList is within a valid range.
   • Adds the new node at the position indicated by emptyList.
   • Updates pointers to maintain the linked list structure.

Main Program

linkedList = [
    node(1, 1), node(5, 4), node(6, 7), node(7, -1), node(2, 2),
    node(0, 6), node(0, 8), node(56, 3), node(0, 9), node(0, -1)
]
startPointer = 0
emptyList = 5

outputNodes(linkedList, startPointer)
returnValue = addNode(linkedList, startPointer, emptyList)

if returnValue:
    print("Item successfully added")
else:
    print("Item not added, list full")

outputNodes(linkedList, startPointer)

1. Linked List Initialization: Defines a list of nodes with initial data and pointers.
2. Start and Empty Pointers: Defines startPointer (beginning of the list) and emptyList (first available spot for a new node).
3. Function Calls:
   • outputNodes: Outputs the current state of the linked list.
   • addNode: Adds a new node based on user input.
4. Result Check:
   • Prints appropriate message based on whether a new node was successfully added.
   • Outputs the updated state of the linked list.

Key Concepts

• Linked List: A data structure consisting of nodes where each node contains data and a reference to the next node.
• Nodes: Fundamental entities storing the actual data and pointer to the next node.
• Pointers: Variables storing the position of nodes, used to traverse and manipulate the list.

Additional Example

linkedList = [
    node(1, -1), node(None, -1), node(None, -1), node(None, -1),
    node(None, -1), node(None, -1)
]
startPointer = 0
emptyList = 1

outputNodes(linkedList, startPointer)
addNode(linkedList, startPointer, emptyList)
outputNodes(linkedList, startPointer)

This example uses a minimal linked list setup to illustrate similar operations with different node data and structure.