feat: Add Hierholzer's Algorithm for Eulerian Circuits

src/test/java/com/thealgorithms/graph/HierholzerAlgorithmTest.java

@@ -1,22 +1,14 @@
 package com.thealgorithms.graph;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertFalse;
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
-import java.util.Arrays;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
+import static org.junit.jupiter.api.Assertions.*;
+import java.util.*;
 import org.junit.jupiter.api.Test;
 
 public class HierholzerAlgorithmTest {
 
     @Test
     public void testFindsEulerianCircuitInSimpleTriangleGraph() {
-        // Create a simple triangle graph where a circuit definitely exists: 0-1, 1-2, 2-0
+        // A simple triangle graph where a circuit definitely exists: 0-1, 1-2, 2-0
         Map<Integer, LinkedList<Integer>> graph = new HashMap<>();
         graph.put(0, new LinkedList<>(Arrays.asList(1, 2)));
         graph.put(1, new LinkedList<>(Arrays.asList(0, 2)));
@@ -50,7 +42,7 @@ public void testFailsForGraphWithOddDegreeVertices() {
         // The find method should return an empty list
         assertTrue(algorithm.findEulerianCircuit().isEmpty());
     }
-
+    
     @Test
     public void testFailsForDisconnectedGraph() {
         // Create a graph with two separate triangles (0-1-2 and 3-4-5)