How to Fix a Singly Linked List Duplicate Deletion Issue in C

Описание: Learn how to solve a common problem when attempting to delete duplicate nodes from a `singly linked list` in C with a clear code example and detailed explanation.
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This video is based on the question https://stackoverflow.com/q/68040287/ asked by the user 'roshannepal_x' ( https://stackoverflow.com/u/16055353/ ) and on the answer https://stackoverflow.com/a/68040630/ provided by the user 'Geoduck' ( https://stackoverflow.com/u/3991211/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: Deleting Duplicates in a Singly Linked List

If you’re working with linked lists in C, you might encounter situations where you need to remove duplicate nodes from a sorted list. This problem can be tricky, especially if the logic in your while loop doesn’t work as expected. Let's dive into a common issue and how we can resolve it effectively.

In this post, we will look at the problem of deleting nodes with the same data from a sorted singly linked list. We will examine the candidate code where the while loop is executed only once, and discuss the key changes needed to fix it.

Code Overview: Current Implementation

The provided main function aims to set up a linked list, populate it with values, and delete duplicate values. Here’s a brief recount of the provided functionality and code snippets:

Insertion and Printing Functions

Inserting Nodes: You have an Insert function that adds new nodes at the beginning of the linked list.

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Printing Nodes: The Print function is responsible for displaying the linked list contents.

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Deletion Logic Issues

Inside the main function, the intention is to delete duplicates. However, an issue arises with the implementation of the while loop that checks for duplicates. It’s crucial to ensure that you handle the head of the list properly and check for NULL values effectively.

Solution: Revised Code Snippet

To effectively remove duplicates, we need a streamlined approach that handles pointer updates correctly and ensures we check nodes for duplication in the right sequence. Here’s a corrected version of the deletion logic:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Explained

Next Pointer Handling: We introduced a next pointer that starts as the node following Head. This pointer helps in checking and skipping duplicates effectively.

Proper NULL Checks: The condition next != NULL ensures we don’t dereference a NULL pointer, which can cause a crash.

Memory Management: We added a call to free(next); ensuring that we properly free the memory of any duplicate nodes that are removed.

Sequential Movement of Head: After processing duplicates, we move Head to the next distinct element in the list.

Conclusion

By following the revised approach for deleting duplicates, you can efficiently clean your singly linked list while avoiding common pitfalls associated with pointer chain management and memory allocation. Implement these practices, and your program will handle duplicate entries more gracefully.

Feel free to try implementing this adjustment in your code and watch how efficiently your linked list operates while managing duplicates effectively!