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feat: Add Hierholzer's Algorithm for Eulerian Circuits #6726

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feat: Add Hierholzer's Algorithm for Eulerian Circuits #6726

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sairamsharan
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  • I have read CONTRIBUTING.md.
  • This pull request is all my own work -- I have not plagiarized it.
  • All filenames are in PascalCase.
  • All functions and variable names follow Java naming conventions.
  • All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
  • All new code is formatted with clang-format -i --style=file path/to/your/file.java

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codecov-commenter commented Oct 10, 2025 •
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Codecov Report

❌ Patch coverage is 76.56250% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.33%. Comparing base (f0fb971) to head (ef458a2).
⚠️ Report is 12 commits behind head on master.

Files with missing lines Patch % Lines
...a/com/thealgorithms/graph/HierholzerAlgorithm.java 76.56% 5 Missing and 10 partials ⚠️
Additional details and impacted files 
@@             Coverage Diff              @@
##             master    #6726      +/-   ##
============================================
+ Coverage     76.80%   77.33%   +0.52%     
- Complexity     6047     6189     +142     
============================================
  Files           719      722       +3     
  Lines         20342    20653     +311     
  Branches       3940     4010      +70     
============================================
+ Hits          15624    15971     +347     
+ Misses         4127     4060      -67     
- Partials        591      622      +31

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@sairamsharan sairamsharan force-pushed the feat-hierholzer-algorithm branch from cc180be to 568913c Compare October 11, 2025 06:36
@sairamsharan sairamsharan force-pushed the feat-hierholzer-algorithm branch from d24cf14 to 96bd4fc Compare October 11, 2025 07:01
DenizAltunkapan
DenizAltunkapan reviewed Oct 12, 2025
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@sairamsharan Thank you for your contribution. Please remove ChatGPT-like "FINAL FIX" comments.

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java
import java.util.Map;
import java.util.Set;
import java.util.Stack;

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Please add proper JavaDoc comments explaining this algorithm, its purpose, and expected input (e.g., undirected graph), similar to other classes in the repository.

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java

private final Map<Integer, LinkedList<Integer>> graph;

public HierholzerAlgorithm(Map<Integer, LinkedList<Integer>> graph) {
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Consider mentioning in JavaDoc that an undirected graph is expected, if it is so.

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java Outdated
tempGraph.get(nextVertex).remove(Integer.valueOf(currentVertex));
currentPath.push(nextVertex);
} else {
circuit.add(0, currentPath.pop());
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Consider using LinkedList.addFirst() for better performance.

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java Outdated

dfs(startNode, visited);

// FINAL FIX: Use entrySet for efficiency.
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why "FINAL FIX:" ? I think this comment might be confusing...

src/main/java/com/thealgorithms/graph/HierholzerAlgorithm.java Outdated
List<Integer> circuit = new LinkedList<>();

int startVertex = -1;
// FINAL FIX: Use entrySet for efficiency.
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why "FINAL FIX:" ? I think this comment might be confusing...

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@yanglbme yanglbme Awaiting requested review from yanglbme yanglbme is a code owner

@alxkm alxkm Awaiting requested review from alxkm alxkm is a code owner

@DenizAltunkapan DenizAltunkapan Awaiting requested review from DenizAltunkapan DenizAltunkapan is a code owner

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@sairamsharan @codecov-commenter @DenizAltunkapan