code: package edu.cmu.ml.rtw.pra.features;
  
  import java.util.Arrays;
  
  public class Path {
    private int[] nodes;
    private int[] edges;
    private boolean[] reverse;
    private int startNode;
    private int hops;
  
    public Path(int startNode, int maxHops) {
      this.startNode = startNode;
      hops = 0;
      nodes = new int[maxHops];
      edges = new int[maxHops];
      reverse = new boolean[maxHops];
    }
  
    public void addHop(int node, int edge, boolean rev) {
      nodes[hops] = node;
      edges[hops] = edge;
      reverse[hops] = rev;
      hops++;
    }
  
    public boolean alreadyVisited(int node) {
      // We could try to be smart with some kind of binary search, or something, but while MAX_HOPS
      // is around 10 (and generally the number of actual hops is 5 or less), it seems like this
      // should be fast enough.
      if (node == startNode) {
        return true;
      }
      for (int i=0; i<hops; i++) {
        if (nodes[i] == node)
          return true;
      }
      return false;
    }
  
    public int[] getNodes() {
      int[] seenNodes = new int[hops];
      System.arraycopy(nodes, 0, seenNodes, 0, hops);
      return seenNodes;
    }
  
    public int[] getEdges() {
      int[] seenEdges = new int[hops];
      System.arraycopy(edges, 0, seenEdges, 0, hops);
      return seenEdges;
    }
  
    public boolean[] getReverse() {
      boolean[] seenReverse = new boolean[hops];
      System.arraycopy(reverse, 0, seenReverse, 0, hops);
      return seenReverse;
    }
  
    public int getStartNode() {
      return startNode;
    }
  
    public int getHops() {
      return hops;
    }
  
    public int getLastEdgeType() {
      if (hops == 0) return -1;
      return edges[hops - 1];
    }
  
    @Override
    public String toString() {
      String result = "" + startNode;
      for (int i = 0; i < hops; i ++) {
        result += "-";
        if (reverse[i]) {
          result += "_";
        }
        result += edges[i] + "->" + nodes[i];
      }
      return result;
    }
  
    @Override
    public int hashCode() {
      final int prime = 31;
      int result = 1;
      result = prime * result + Arrays.hashCode(edges);
      result = prime * result + hops;
      result = prime * result + Arrays.hashCode(nodes);
      result = prime * result + Arrays.hashCode(reverse);
      result = prime * result + startNode;
      return result;
    }
  
    @Override
    public boolean equals(Object obj) {
      if (this == obj)
        return true;
      if (obj == null)
        return false;
      if (getClass() != obj.getClass())
        return false;
      Path other = (Path) obj;
      if (!Arrays.equals(edges, other.edges))
        return false;
      if (hops != other.hops)
        return false;
      if (!Arrays.equals(nodes, other.nodes))
        return false;
      if (!Arrays.equals(reverse, other.reverse))
        return false;
      if (startNode != other.startNode)
        return false;
      return true;
    }
  }
  