Finished

src/Build.java

@@ -1,3 +1,4 @@
+import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
@@ -14,6 +15,31 @@ public class Build {
    * @param k the maximum word length (exclusive)
    */
   public static void printShortWords(Vertex<String> vertex, int k) {
+    Set<Vertex<String>> set = new HashSet<>();
+
+    printSHortWordsHelper(set, k, vertex);
+  }
+
+  public static void printSHortWordsHelper(Set<Vertex<String>> current, int k, Vertex<String> vertex)
+  {
+    if(vertex == null || current.contains(vertex))
+    {
+      return;
+    }
+
+    current.add(vertex);
+
+    String name = vertex.data;
+    if(name.length() < k)
+    {
+      System.out.println(name);
+    }
+
+    for(Vertex<String> item : vertex.neighbors)
+    {
+      printSHortWordsHelper(current, k, item);
+    }
+
   }
 
   /**
@@ -23,7 +49,40 @@ public static void printShortWords(Vertex<String> vertex, int k) {
    * @return the longest reachable word, or an empty string if the vertex is null
    */
   public static String longestWord(Vertex<String> vertex) {
-    return "";
+    if(vertex == null) return "";
+
+    Set<Vertex<String>> set = new HashSet<>();
+
+    return longestWordHelper(set, vertex, vertex.data);
+  }
+
+  public static String longestWordHelper(Set<Vertex<String>> set, Vertex<String> vertex, String word)
+  {
+
+    if(vertex == null || set.contains(vertex)) return "";
+
+    set.add(vertex);
+
+    String newWord = "";
+    if(word.length() < vertex.data.length())
+    {
+      newWord = vertex.data;
+    }
+    else
+    {
+      newWord = word;
+    }
+
+    for(Vertex<String> item : vertex.neighbors)
+    {
+     String longestNeighbor = longestWordHelper(set, item, newWord);
+     if(longestNeighbor.length() > newWord.length())
+     {
+      newWord = longestNeighbor;
+     }
+    }
+
+    return newWord;
   }
 
   /**
@@ -34,6 +93,29 @@ public static String longestWord(Vertex<String> vertex) {
    * @param <T> the type of values stored in the vertices
    */
   public static <T> void printSelfLoopers(Vertex<T> vertex) {
+    if(vertex == null) return;
+
+    Set<Vertex<T>> set = new HashSet<>();
+
+    printSelfLoopersHelper(vertex, set);
+  }
+
+
+  public static <T> void printSelfLoopersHelper(Vertex<T> vertex, Set<Vertex<T>> set)
+  {
+    if(set.contains(vertex)) return;
+
+    set.add(vertex);
+
+    if(vertex.neighbors.contains(vertex))
+    {
+      System.out.println(vertex.data);
+    }
+
+    for(Vertex<T> item : vertex.neighbors)
+    {
+      printSelfLoopersHelper(item, set);
+    }
   }
 
   /**
@@ -45,6 +127,27 @@ public static <T> void printSelfLoopers(Vertex<T> vertex) {
    * @return true if the destination is reachable from the start, false otherwise
    */
   public static boolean canReach(Airport start, Airport destination) {
+    Set<Airport> set = new HashSet<>();
+
+    return canReachHelper(start, destination, set);
+  }
+
+  public static boolean canReachHelper(Airport start, Airport des, Set<Airport> set)
+  {
+    if(start == des) return true;
+
+    set.add(start);
+
+    for(Airport item: start.getOutboundFlights())
+    {
+      if(!set.contains(item) && item.getAirportCode() != start.getAirportCode())
+      {
+        if(canReachHelper(item, des, set) == true)
+        {
+          return true;
+        }
+      }
+    }
     return false;
   }
 
@@ -58,6 +161,25 @@ public static boolean canReach(Airport start, Airport destination) {
    * @return a set of values that cannot be reached from the starting value
    */
   public static <T> Set<T> unreachable(Map<T, List<T>> graph, T starting) {
-    return new HashSet<>();
+    Set<T> set = new HashSet<>();
+    unreachableHelper(starting, graph, set);
+
+    Set<T> unreachable = new HashSet<>(graph.keySet());
+    unreachable.removeAll(set);
+
+    return unreachable;
+  }
+
+  public static <T> void unreachableHelper(T current, Map<T, List<T>> graph, Set<T> visted)
+  {
+    if(current == null || visted.contains(current)) return;
+
+    visted.add(current);
+
+    for(T item: graph.getOrDefault(current, Collections.emptyList()))
+    {
+      unreachableHelper(item, graph, visted);
+    }
   }
+
 }