diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..2d2fbec 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,115 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: best case O(log n) / worst case O(n)
+  # Space Complexity: O(n)
+  def add_helper(current, new_node)
+    return new_node if current.nil?
+
+    if new_node.key <= current.key
+      current.left = add_helper(current.left, new_node)
+    else
+      current.right = add_helper(current.right, new_node)
+    end
+
+    return current
+  end
+
   def add(key, value)
-    raise NotImplementedError
+    new_node = TreeNode.new(key, value)
+
+    if @root.nil?
+      @root = new_node
+    else
+      add_helper(@root, new_node)
+    end
+
+    return @root
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: best case O(log n) / worst case O(n)
+  # Space Complexity: O(n)
   def find(key)
-    raise NotImplementedError
+    current = @root
+    return nil if current.nil?
+
+    if current.key == key
+      return current.value
+    else
+      if key < current.key
+        return current.left.value
+      else
+        return current.right.value
+      end
+    end
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def inorder_helper(current, order)
+    if current.nil?
+      return
+    end
+
+    inorder_helper(current.left, order) if current.left
+    order << {key: current.key, value: current.value}
+    inorder_helper(current.right, order)  if current.right
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def inorder
-    raise NotImplementedError
+    order = []
+    inorder_helper(@root, order)
+    return order
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def preorder_helper(current, order)
+    if current.nil?
+      return
+    end
+
+    order << {key: current.key, value: current.value}
+    preorder_helper(current.left, order) if current.left
+    preorder_helper(current.right, order) if current.right
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def preorder
-    raise NotImplementedError
+    order = []
+    preorder_helper(@root, order)
+    return order
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def postorder_helper(current, order)
+    if current.nil?
+      return
+    end
+
+    postorder_helper(current.left, order) if current.left
+    postorder_helper(current.right, order) if current.right
+    order << {key: current.key, value: current.value}
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def postorder
-    raise NotImplementedError
+    order = []
+    postorder_helper(@root, order)
+    return order
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def height_helper(current)
+    if current.nil?
+      return 0
+    else
+      return 1 + [height_helper(current.left), height_helper(current.right)].max
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def height
-    raise NotImplementedError
+    height_helper(@root)
   end
 
   # Optional Method
@@ -64,3 +139,4 @@ def to_s
     return "#{self.inorder}"
   end
 end
+