Деревья(Центроид)

vol6/src/main/java/ru/mifi/practice/vol6/tree/Centroid.java

@@ -0,0 +1,62 @@
+package ru.mifi.practice.vol6.tree;
+
+import ru.mifi.practice.vol6.tree.visitors.Count;
+
+@SuppressWarnings("PMD.SingularField")
+public final class Centroid<T> implements Visitor<T> {
+    private Node<T> centroid = null;
+    private int vertexes = 0;
+
+    private static <T> int nodeCount(Node<T> node, Count<T> count, VisitorStrategy.PreOrder<T> strategy) {
+        count.clear();
+        if (node == null) {
+            return 0;
+        }
+        node.visit(count, strategy);
+        return count.count();
+    }
+
+    private static <T> int nodeUpper(Node<T> node, Count<T> count, VisitorStrategy.PreOrder<T> strategy) {
+        count.clear();
+        VisitorStrategy.AlreadyVisited<T> alreadyVisited = new VisitorStrategy.AlreadyVisited<>(strategy);
+        alreadyVisited.put(node);
+        Node<T> it = node.parent();
+        while (it != null) {
+            it.visit(count, alreadyVisited);
+            it = it.parent();
+        }
+        return count.count();
+    }
+
+    public Node<T> centroid(Tree<T> tree) {
+        centroid = null;
+        VisitorStrategy.PreOrder<T> strategy = new VisitorStrategy.PreOrder<>();
+        Count<T> count = new Count<>();
+        tree.visit(count, strategy);
+        vertexes = count.count();
+        tree.visit(this, strategy);
+        return centroid;
+    }
+
+    @Override
+    public void enterNode(Node<T> node) {
+        VisitorStrategy.PreOrder<T> strategy = new VisitorStrategy.PreOrder<>();
+        Count<T> count = new Count<>();
+        var upper = nodeUpper(node, count, strategy);
+        var left = nodeCount(node.left(), count, strategy);
+        var right = nodeCount(node.right(), count, strategy);
+        if (left <= vertexes / 2 && right <= vertexes / 2 && upper <= vertexes / 2) {
+            centroid = node;
+        }
+    }
+
+    @Override
+    public void exitNode(Node<T> node) {
+        //None
+    }
+
+    @Override
+    public void empty() {
+        //None
+    }
+}

vol6/src/main/java/ru/mifi/practice/vol6/tree/Main.java

@@ -51,5 +51,9 @@ public static void main(String[] args) throws IOException {
         List<Node<Integer>> centered = center.center(tree, integer -> integer);
         System.out.print("CENTR: ");
         System.out.println(centered);
+        Centroid<Integer> centroid = new Centroid<>();
+        var c = centroid.centroid(tree);
+        System.out.print("CEOID: ");
+        System.out.println(c);
     }
 }

vol6/src/main/java/ru/mifi/practice/vol6/tree/VisitorStrategy.java

@@ -22,10 +22,14 @@ public void visit(Node<T> node, Visitor<T> visitor, VisitorStrategy<T> strategy)
             }
             visited.add(node);
             visitor.enterNode(node);
-            this.strategy.visit(node.left(), visitor, strategy);
-            this.strategy.visit(node.right(), visitor, strategy);
+            strategy.visit(node.left(), visitor, this.strategy);
+            strategy.visit(node.right(), visitor, this.strategy);
             visitor.exitNode(node);
         }
+
+        public void put(Node<T> node) {
+            visited.add(node);
+        }
     }
 
     final class PreOrder<T> implements VisitorStrategy<T> {

vol6/src/main/java/ru/mifi/practice/vol6/tree/visitors/Count.java

@@ -30,4 +30,9 @@ public void exitNode(Node<T> node) {
     public void empty() {
         //None
     }
+
+    @Override
+    public String toString() {
+        return String.valueOf(count.intValue());
+    }
 }