finished livecode

src/Traversal.java

@@ -1,5 +1,148 @@
+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);
+
+    TreeNode<String> stringRoot = new TreeNode<String>("hello", null, null);
+    stringRoot.left = new TreeNode<String>("how", null, null);
+    stringRoot.left.left = new TreeNode<String>("are", 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>("am", 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<=50000; i++) {
+      current.right = new TreeNode<Integer>(i, null, null);
+      current = current.right;
+    }
+
+    // preOrderIter(megaRoot);
+    levelOrder(stringRoot);
+
+    // System.out.println("Preorder recursive");
+    // preorder(root);
+    // System.out.println("Preorder iterative");
+    // preOrderIter(root);
+
+    // preorder(megaRoot);
+    // preorder(root);
+    // postorder(root);
+    // inorder(stringRoot);
+    // printGreater(root, 1);
+    // System.out.println(countNodes(root));
+    // Map<String, Integer> counts = new HashMap<>();
+    // System.out.println(toMap(stringRoot));
+  }
+
+  // Print a tree rooted at the given node in pre-order 
+  public static void preorder(TreeNode<?> node) {
+    // if null, return
+    if(node == null) {
+      return;
+    }
+    // print value
+    System.out.println(node.value);
+    // traverse left
+    preorder(node.left);
+    // traverse right
+    preorder(node.right);
+  }
+
+  public static <T> void preOrderIter(TreeNode<T> node) {
+    Stack<TreeNode<T>> stack = new Stack<>();
+
+    stack.push(node);
+
+    while (!stack.isEmpty()) {
+      TreeNode<T> current = stack.pop();
+
+      if (current == null) continue;
+
+      System.out.println(current.value);
+      stack.push(current.right);
+      stack.push(current.left);
+
+    }
+  }
+
+  public static <T> void levelOrder(TreeNode<T> node) {
+    Queue<TreeNode<T>> stack = new LinkedList<>();
+
+    stack.add(node);
+
+    while (!stack.isEmpty()) {
+      TreeNode<T> current = stack.poll();
+
+      if (current == null) continue;
+
+      System.out.println(current.value);
+      stack.add(current.left);
+      stack.add(current.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> Map<T, Integer> toMap(TreeNode<T> node, Map <T, Integer> counts) {
+    if (node == null) {
+      return counts;
+    }
+    counts.put(node.value, counts.getOrDefault(node.value, 0) + 1 );
+    toMap(node.left, counts);
+    toMap(node.right, counts);
+    return counts;
+  }
+
+  public static int countNodes(TreeNode<?> node){
+
+    if (node == null) return 0;
+    return 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 void postorder(TreeNode<?> node){
+    if (node == null) return;
+    postorder(node.left);
+    postorder(node.right);
+    System.out.println(node.value);
+  }
+
+  public static void inorder(TreeNode<?> node){
+    if (node == null) return;
 
+    inorder(node.left);
+    System.out.println(node.value);
+    inorder(node.right);
   }
 }

src/TreeNode.java

@@ -1,4 +1,11 @@
-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;
+  }
 }