Adding a Node to a Linked List in Python

Code Explanation: Adding a Node to a Linked List

Overview

The provided Python function, addNode, adds a new node to a linked list. This operation involves user input to determine the data for the new node, and the linked list is likely implemented with an array where each element contains a node object.

Below is a deconstructed explanation of the code.

Code Breakdown

def addNode(linkedList, currentPointer, emptyList):
    dataToAdd = input("Enter the data to add")
    if emptyList < 0 or emptyList > 9:
        return False
    else:
        newNode = node(int(dataToAdd), -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. Function Signature

• Function Name: addNode
• Parameters:
  • linkedList: An array representation of the linked list.
  • currentPointer: The index of the current node in the list.
  • emptyList: The index of the first available slot in the linkedList array where the new node can be added.

2. User Input for Data

The variable dataToAdd captures user input for the new node's data.

dataToAdd = input("Enter the data to add")

3. Validation of emptyList

The function checks that emptyList is within a valid index range (0 to 9). If not, the function returns False.

if emptyList < 0 or emptyList > 9:
    return False

4. Node Creation

• If the validation passes, a new node is created.
• The node constructor takes two arguments:
  • The data converted to an integer.
  • A pointer to the next node, initially set to -1 (indicating no next node).

newNode = node(int(dataToAdd), -1)
linkedList[emptyList] = newNode

5. Finding the End of the Linked List

A loop traverses the linked list to find the last node (the node which has a nextNode value of -1).

previousPointer = 0
while(currentPointer != -1):
    previousPointer = currentPointer
    currentPointer = linkedList[currentPointer].nextNode

6. Linking the New Node

• The nextNode of the last node is updated to point to emptyList, thus linking the new node.
• The emptyList pointer is updated to the next available slot in the list.

linkedList[previousPointer].nextNode = emptyList
emptyList = linkedList[emptyList].nextNode

7. Function Return

The function concludes by returning True, indicating that the node has been successfully added.

return True

Key Concepts

• Linked List: A data structure consisting of nodes, each containing data and a pointer to the next node.
• Node: A fundamental unit of a linked list which contains a data part and a pointer to the next node.
• Pointer: An index or reference indicating a node's position in the data structure.

Additional Considerations

1. Error Handling: The code has basic error handling for the emptyList index. However, additional checks might be useful to ensure input conversion and node creation succeed without issues.
2. Dynamic List Size: The code assumes emptyList indices are within 0 to 9. This constraint should be adaptable for different list sizes.

Additional Example

For a better understanding, suppose a more dynamic approach is needed where the list size is not restricted to 10. This would involve:

• Dynamic resizing of the linked list.
• Error handling for out-of-bounds operations.
• Initializing nextNode properties with the correct pointers.

By adopting these practices, the linked list can accommodate diverse and more complex operational requirements. To master these concepts, consider courses available on the Enterprise DNA Platform.