jeewamp

/**
 * @param adjacencyList, oddVertices, EulerianPath.
 */
public <P extends Integer, Q extends ArrayList<P>> ArrayList<P>
hierholzersAlgorithm(HashMap<P, Q> adjacencyList, ArrayList<P> oddVertices, ArrayList<P> path) {

    P currentVertex=null;
    //If path is not empty, the start vertex should be in the path. 
    //Check if Semi-Eulerian. If yes, start traversing from one of them.
    if(oddVertices.size()==2) {

jeewamp

public class BreadthFirstSearch<K> {

    final Integer WHITE=0; //Not yet discovered
    final Integer GRAY=1;  //Discovered by not all adjacent vertices are discovered.
    final Integer BLACK=2; //Discovered and all adjacent vertices are discovered.

    HashMap<K,Integer> colour = new HashMap<K, Integer>();
    HashMap<K,Integer> distance = new HashMap<K, Integer>();
    HashMap<K, K> predecessor = new HashMap<K, K>();

jeewamp

/**
 * Convert a Non-Eulerian to Semi-Eulerian. If graph is Eulerian or Semi-Eulerian, the graph will be
 * immediately returned.
 * @param adjacencyList, ArrayList of odd Vertices
 * @return
 */
public <P extends Integer, Q extends ArrayList<P>> HashMap<P, Q>
convertToEulerian(HashMap<P, Q> adjacencyList, ArrayList<P> oddVertices){
    if(oddVertices.size()<=2)
        return adjacencyList;

jeewamp

/**
 * @param adjacencyList of the graph
 * @return ArrayList of oddVertices. if oddVertices is empty its Eulerian,
 * if it has 2 elements its Semi-Eulerian, else its not Eulerian.
 */
public <P extends Integer, Q extends ArrayList<P>> ArrayList<P> checkEulerian(HashMap<P, Q> adjacencyList) {
    ArrayList<P> oddVertices = new ArrayList<P>();
    Iterator iterator = adjacencyList.keySet().iterator();
    while(iterator.hasNext()) {
        P key = (P) iterator.next();

jeewamp

HashMap<Integer,ArrayList<Integer>> adjacencyList = new HashMap<Integer,ArrayList<Integer>>;