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kobukuro
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Feb 19, 2026
kobukuro
commented
- Add clone_graph solution with DFS approach using hash map for visited nodes
- Add 3 test cases covering 4-node graph, single node, and empty graph
- Include deep copy verification helper to ensure proper cloning
- Remove old file from Depth First Search folder
- Add clone_graph solution with DFS approach using hash map for visited nodes - Add 3 test cases covering 4-node graph, single node, and empty graph - Include deep copy verification helper to ensure proper cloning - Remove old file from Depth First Search folder
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Pull request overview
This PR adds a solution for LeetCode problem 133 (Clone Graph) using a depth-first search approach with hash map memoization. The solution correctly implements graph cloning by maintaining a mapping of original nodes to their clones to handle cycles and shared references.
Changes:
- Add DFS-based clone_graph solution with hash map for tracking visited nodes
- Add comprehensive test suite with deep copy verification helper
- Cover three test cases: 4-node cyclic graph, single node, and empty graph
Reviewed changes
Copilot reviewed 3 out of 4 changed files in this pull request and generated 4 comments.
| File | Description |
|---|---|
| problems/medium/clone_graph_133/solution.py | Implements Node class and clone_graph solution using DFS with mapping dictionary |
| problems/medium/clone_graph_133/test_solution.py | Test suite with setup_method pattern and custom deep copy verification |
| problems/medium/clone_graph_133/init.py | Empty init file following project structure |
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| class Solution: | ||
| def clone_graph(self, node: 'Node', mapping=None) -> Optional['Node']: |
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The mapping parameter should not be part of the public API. Exposing internal state as an optional parameter can lead to confusion and misuse. Consider using a nested helper function that takes the mapping parameter, while keeping the public clone_graph method with only the node parameter. This is the pattern used in other DFS solutions in the codebase like word_search_79 and course_schedule_207.
- Fix grammar: change "a number of" to "the number of" - Add comma for better sentence structure - Use present tense instead of conditional tense - Clarify worst-case recursion stack scenario with example
- Move `if node is None` check to function start - Avoid unnecessary operations when input is None - Align with early exit best practice
Co-authored-by: kobukuro <9405082+kobukuro@users.noreply.github.com>
Co-authored-by: kobukuro <9405082+kobukuro@users.noreply.github.com>
Fix unused visited_clone variable in clone graph test verification
