Complete

src/Build.java

@@ -14,6 +14,19 @@ public class Build {
    * @param k the maximum word length (exclusive)
    */
   public static void printShortWords(Vertex<String> vertex, int k) {
+    Set<Vertex<String>> visit = new HashSet<>();
+    printShortWords(vertex, k, visit);
+  }
+  public static void printShortWords(Vertex<String> vertex, int k, Set<Vertex<String>> visited) {
+    if(vertex == null || visited.contains(vertex)) return;
+    visited.add(vertex);
+    String word = vertex.data;
+    if(word.toCharArray().length < k) {
+      System.out.println(word);
+    }
+    for(Vertex<String> newWords : vertex.neighbors) {
+      printShortWords(newWords, k, visited);
+    }
   }
 
   /**
@@ -23,7 +36,18 @@ 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 "";
+    Set<Vertex<String>> visit = new HashSet<>();
+    return longestWord(vertex, visit, "");
+  }
+  public static String longestWord(Vertex<String> vertex, Set<Vertex<String>> visited, String max) {
+    if(vertex == null || visited.contains(vertex)) return "";
+    visited.add(vertex);
+    if(max.length() < vertex.data.length()) max = vertex.data;
+    for(Vertex<String> word : vertex.neighbors) {
+      String newWord = longestWord(word, visited, max);
+      if(newWord.length() > max.length()) max = newWord;
+    }
+    return max;
   }
 
   /**
@@ -34,6 +58,18 @@ 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) {
+    Set<Vertex<T>> set = new HashSet<>();
+    printSelfLoopers(vertex, set);
+  }
+  public static <T> void printSelfLoopers(Vertex<T> vertex, Set<Vertex<T>> visit) {
+    if(vertex == null || visit.contains(vertex)) return;
+    visit.add(vertex);
+    for(Vertex<T> neighbor : vertex.neighbors) {
+      if(neighbor == vertex) {
+        System.out.println(vertex.data);
+      }
+      printSelfLoopers(neighbor, visit);
+    }
   }
 
   /**
@@ -45,6 +81,16 @@ 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> visit = new HashSet<>();
+    return canReach(start, destination, visit);
+  }
+  public static boolean canReach(Airport start, Airport destination, Set<Airport> visited) {
+    if(start == null || destination == null || visited.contains(start)) return false;
+    visited.add(start);
+    for(Airport next : start.getOutboundFlights()) {
+      canReach(next, destination, visited);
+    }
+    if(visited.contains(destination)) return true;
     return false;
   }
 
@@ -58,6 +104,27 @@ 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> seen = new HashSet<>();
+    Set<T> unseen = new HashSet<>();
+    return unreachable(graph, starting, seen, unseen);
+  }
+  public static <T> Set<T> unreachable(Map<T, List<T>> graph, T starting, Set<T> visited, Set<T> unseen) {
+    if(graph == null || starting == null || visited.contains(starting)) return new HashSet<>();
+    if(!graph.containsKey(starting)) {
+      return graph.keySet();
+    }
+
+    visited.add(starting);
+    for(T next : graph.get(starting)) {
+      unreachable(graph, next, visited, unseen);
+    }
+
+    unseen.clear();
+    for(T allPoint : graph.keySet()) {
+      if(!visited.contains(allPoint)) {
+        unseen.add(allPoint);
+      }
+    }
+    return unseen;
   }
 }