In class TreeNode live code

src/Traversal.java

@@ -1,5 +1,164 @@
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.Map;
+import java.util.Queue;
+import java.util.Stack;
+
 public class Traversal {
   public static void main(String[] args) {
+    TreeNode<Integer> root = new TreeNode<Integer>(10, null, null);
+    root.left = new TreeNode<Integer>(9, null, null);
+    root.left.left = new TreeNode<Integer>(5, null, null);
+    root.left.right = new TreeNode<Integer>(2, null, null);
+
+    root.right = new TreeNode<Integer>(15, null, null);
+    root.right.left = new TreeNode<Integer>(-3, null, null);
+    root.right.right = new TreeNode<Integer>(5, null, null);
+    root.right.right.right = new TreeNode<Integer>(22, null, null);
+
+    TreeNode<String> stringRoot = new TreeNode<String>("hello", null, null);
+    stringRoot.left = new TreeNode<String>("how", null, null);
+    stringRoot.left.left = new TreeNode<String>("hello", null, null);
+    stringRoot.left.right = new TreeNode<String>("you", null, null);
+
+    stringRoot.right = new TreeNode<String>("I", null, null);
+    stringRoot.right.left = new TreeNode<String>("I", null, null);
+    stringRoot.right.right = new TreeNode<String>("so", null, null);
+    stringRoot.right.right.right = new TreeNode<String>("good", null, null);
+
+    TreeNode<Integer> megaRoot = new TreeNode<Integer>(1, null, null);
+    TreeNode<Integer> current = megaRoot;
+
+    for (int i = 2; i <= 5000; i++) {
+      current.right = new TreeNode<Integer>(i, null, null);
+      current = current.right;
+    }
+
+    // preorder(root);
+    // postorder(root);
+    // inorder(root);
+    // printGreater(root, 4);
+    // System.out.println(countNodes(root));
+    // Map<String, Integer> counts = new HashMap<>();
+    // System.out.println(toMap(stringRoot));
+    // preOrderIter(megaRoot);
+
+    System.out.println("Preorder recuresive");
+    preorder(root);
+    System.out.println("Preorder iterative");
+    // preOrderIter(root);
+    leverOrder(root);
+
+  }
+
+  public static <T> void leverOrder(TreeNode<T> node) {
+    Queue<TreeNode<T>> queue = new LinkedList<>();
+
+    queue.add(node);
+    while (!queue.isEmpty()) {
+      TreeNode<T> current = queue.poll();
+
+      if (current == null) {
+        continue; // move to the top of the loop
+      }
+
+      System.out.println(current.value);
+      queue.add(current.left);
+      queue.add(current.right);
+
+    }
+
+  }
+
+  public static <T> void preOrderIter(TreeNode<T> node) {
+    Stack<TreeNode<T>> stack = new Stack<>();
+
+    stack.push(node);
+    while (!stack.empty()) {
+      TreeNode<T> current = stack.pop();
+
+      if (current == null) {
+        continue; // move to the top of the loop
+      }
+
+      System.out.println(current.value);
+      stack.push(current.right);
+      stack.push(current.left);
+
+    }
+
+  }
+
+  // print tree rooted at the given node in pre-order
+  public static void preorder(TreeNode<?> node) {
+
+    if (node == null)
+      return;
+    System.out.println(node.value);
+    preorder(node.left);
+    preorder(node.right);
+
+  }
+
+  public static <T> Map<T, Integer> toMap(TreeNode<T> node) {
+    Map<T, Integer> counts = new HashMap<>();
+    toMap(node, counts);
+    return counts;
+
+  }
+
+  private static <T> void toMap(TreeNode<T> node, Map<T, Integer> counts) {
+
+    if (node == null)
+      return;
+    // Fill up the counts
+    counts.put(node.value, counts.getOrDefault(node.value, 0) + 1);
+    toMap(node.left, counts);
+    toMap(node.right, counts);
+
+  }
+
+  public static int countNodes(TreeNode<?> node) {
+    // if (node == null) return 0;
+    // if (node == null)
+    // return 0;
+    return node == null ? 0 : countNodes(node.left) + countNodes(node.right) + 1;
+    // int leftCount = countNodes(node.left);
+    // int rightCount = countNodes(node.right);
+    // int overAllCount = leftCount + rightCount + 1;
+    // return overAllCount;
 
   }
+
+  public static void printGreater(TreeNode<Integer> node, int threshold) {
+
+    if (node == null)
+      return;
+    if (node.value > threshold) {
+      System.out.println(node.value);
+    }
+    printGreater(node.left, threshold);
+    printGreater(node.right, threshold);
+
+  }
+
+  public static <T> void postorder(TreeNode<T> node) {
+
+    if (node == null)
+      return;
+    postorder(node.left);
+    postorder(node.right);
+    System.out.println(node.value);
+
+  }
+
+  public static <E> void inorder(TreeNode<E> node) {
+    if (node == null)
+      return;
+    inorder(node.left);
+    System.out.println(node.value);
+    inorder(node.right);
+
+  }
+
 }

src/TreeNode.java

@@ -1,4 +1,13 @@
-public class TreeNode {
+public class TreeNode<T> {
+
+ public T value;
+ public TreeNode<T> left;
+ public TreeNode<T> right;
+
+ public TreeNode(T value, TreeNode<T> left, TreeNode<T> right) {
+  this.value = value;
+  this.left = left;
+  this.right = right;
+ }
 
-
 }