diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..76509e4 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,118 @@ def initialize
     @root = nil
   end
 
+  def add_helper(curr_node, key, value)
+    if curr_node.nil?
+      return TreeNode.new(key, value)
+    else
+      if key < curr_node.key
+        curr_node.left = add_helper(curr_node.left, key, value)
+      else
+        curr_node.right = add_helper(curr_node.right, key, value)
+      end
+    end
+
+    return curr_node
+  end
+
   # Time Complexity: 
   # Space Complexity: 
-  def add(key, value)
-    raise NotImplementedError
+  def add(key, value)    
+    @root = add_helper(@root, key, value)
   end
 
+  def find_helper(curr_node, key)
+    if curr_node.nil?
+      return nil
+    end
+
+    if curr_node.key == key
+      return curr_node.value
+    end
+
+    if curr_node.key > key
+      return find_helper(curr_node.left, key)
+    elsif curr_node.key < key
+      return find_helper(curr_node.right, key)
+    end
+    
+    return nil
+  end 
+
   # Time Complexity: 
   # Space Complexity: 
   def find(key)
-    raise NotImplementedError
+    return find_helper(@root, key)
+  end
+
+  def inorder_helper(current_node, list) 
+    return list if current_node.nil? 
+
+    inorder_helper(current_node.left, list)
+    list << {key: current_node.key, value: current_node.value}
+
+    inorder_helper(current_node.right, list)
+    return list
   end
 
   # Time Complexity: 
   # Space Complexity: 
-  def inorder
-    raise NotImplementedError
+  def inorder(node,)
+    list = []
+    inorder_helper(@root, list)
   end
 
   # Time Complexity: 
   # Space Complexity: 
-  def preorder
-    raise NotImplementedError
+  def preorder_helper(current_node, list) 
+    return list if current_node.nil? 
+    list << {key: current_node.key, value: current_node.value}
+
+    preorder_helper(current_node.left, list)
+    preorder_helper(current_node.right, list)
+
+    return list 
+  end 
+
+  def pre_order
+    list = []
+    return preorder_helper(@root, list)
   end
 
   # Time Complexity: 
   # Space Complexity: 
+  def postorder_helper(current_node, list)
+    return [] if current_node.nil?
+
+    postorder_helper(current_node.left, list)
+    postorder_helper(current_node.right, list)
+    list << {key: current_node.key, value: current_node.value}
+    return list
+  end 
+
   def postorder
-    raise NotImplementedError
+    list = []
+    return postorder_helper(@root, list)
   end
 
+  def height_helper(current_node)
+    return 0 if current_node.nil? 
+
+    left_height = height_helper(current_node.left)
+    right_height = height_helper(current_node.right)
+
+    if left_height > right_height
+      return left_height + 1
+    else
+      return right_height + 1
+    end 
+  end 
+
   # Time Complexity: 
   # Space Complexity: 
   def height
-    raise NotImplementedError
+    height = 0
+    return height_helper(@root)
   end
 
   # Optional Method