Implement skip list#4

Open

AliQassab wants to merge 2 commits intomainfrom

implement-skip-list

Owner

AliQassab commented Mar 8, 2026 •

edited

Loading

Learners, PR Template

Self checklist

I have titled my PR with Region | Cohort | FirstName LastName | Sprint | Assignment Title
My changes meet the requirements of the task
I have tested my changes
My changes follow the style guide

Changelist

Briefly explain your PR.

Questions

Ask any questions you have for your reviewer.

AliQassab added 2 commits

October 18, 2025 11:26


          Implement skip list

775ae3c


          fix: use skip list nodes instead of list.insert for O(log n) insertion

db405a1

AliQassab added the needreview label

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

5 similar comments

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

AliQassab closed this

AliQassab reopened this

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

AliQassab closed this

AliQassab reopened this

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

AliQassab closed this

AliQassab reopened this

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

AliQassab closed this

AliQassab reopened this

github-actions bot commented Mar 8, 2026

Your PR couldn't be matched to an assignment in this module.

Please check its title is in the correct format, and that you only have one PR per assignment.

If this PR is not coursework, please add the NotCoursework label (and message on Slack in #cyf-curriculum or it will probably not be noticed).

If this PR needs reviewed, please add the 'Needs Review' label to this PR after you have resolved the issues listed above.

github-actions bot reviewed

View reviewed changes

github-actions bot left a comment

Good implementation overall! All tests pass and complexity requirements are met. One minor code quality note below.

Sprint-2/implement_skip_list/skip_list.py

+                      self.max_level = 16
+                      self.head = SkipListNode(float('-inf'), self.max_level)
+                      self.level = 0

github-actions bot Mar 8, 2026

This line reassigns current to current.forward[0], but the variable is never read again — making it dead code. It looks like a leftover from a duplicate-check pattern. Since the assignment doesn't require uniqueness you can safely remove this line, or if you do want to guard against duplicates you could add:

Suggested change

      
                    current = current.forward[0]
          
                    if current is not None and current.value == value:
          
                        return  # value already exists, skip duplicate

Either way, leaving an unused variable assignment makes the code harder to read and may mislead future readers into thinking the value is checked.

github-actions bot commented Mar 8, 2026

Code Review Summary

What the trainee did: Implemented a skip list data structure from scratch in Python, supporting insert, contains, and to_list operations, plus a __contains__ dunder method for natural in operator support.

What was done well:

All provided tests pass (both test_single_item and test_general_usage).
Complexity requirements are met: insert and contains are O(log n) average time, and to_list is O(n).
The randomised level generation (_random_level) correctly uses a coin-flip approach, giving the expected probabilistic balance.
The update array pattern for tracking predecessors at each level is correct and idiomatic for skip list implementations.
Good use of float('-inf') as the sentinel head value.
Clean code structure with docstrings on each method.

What needs improvement:

Line 34 — dead code: current = current.forward[0] reassigns the variable but it is never read again. This is most likely a remnant of a duplicate-value guard that was never finished. It does not break anything, but it adds confusion. Either remove it or complete the duplicate check (see inline comment).
No duplicate handling: Inserting the same value twice will silently add two copies, and to_list will return duplicates. This isn't tested in the provided tests and the README doesn't explicitly require uniqueness, but it is worth being aware of.

Overall this is a solid, working skip list implementation. Nice work!

VERDICT: completed

github-actions bot added completed and removed needreview labels

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Labels