diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..a12bad9 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -2,61 +2,108 @@ class TreeNode
   attr_reader :key, :value
   attr_accessor :left, :right
 
-   def initialize(key, val)
+  def initialize(key, val)
     @key = key
     @value = val
     @left = nil
     @right = nil
-   end
+  end
 end
 
 class Tree
   attr_reader :root
+
   def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def add(key, value)
-    raise NotImplementedError
+  # Time Complexity: O(log n) if the tree is balanced, O(n) if the tree is unbalanced
+  #                 - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(1) - constant
+  def add(key, value, current = @root)
+    new_node = TreeNode.new(key, value)
+
+    if @root
+      if key <= current.key
+        current.left ? add(key, value, current.left) : current.left = new_node
+      else
+        current.right ? add(key, value, current.right) : current.right = new_node
+      end
+    else
+      @root = new_node
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def find(key)
-    raise NotImplementedError
+  # Time Complexity: O(log n) if the tree is balance, O(n) is the tree is unbalanced
+  #                 - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(1) - constant
+  def find(key, current = @root)
+    if current
+      if current.key == key
+        return current.value
+      elsif key <= current.key
+        find(key, current.left)
+      elsif key > current.key
+        find(key, current.right)
+      end
+    else
+      return
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def inorder
-    raise NotImplementedError
+  # Time Complexity: O(n) - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(n) where n is equal to the number of TreeNodes in the tree
+  def inorder(current = @root, array = [])
+    if current
+      inorder(current.left, array)
+      array << { key: current.key, value: current.value }
+      inorder(current.right, array)
+    else
+      return array
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def preorder
-    raise NotImplementedError
+  # Time Complexity: O(n) - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(n) where n is equal to the number of TreeNodes in the tree
+  def preorder(current = @root, array = [])
+    if current
+      array << { key: current.key, value: current.value }
+      preorder(current.left, array)
+      preorder(current.right, array)
+    else
+      return array
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def postorder
-    raise NotImplementedError
+  # Time Complexity: O(n) - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(n) where n is equal to the number of TreeNodes in the tree
+  def postorder(current = @root, array = [])
+    if current
+      postorder(current.left, array)
+      postorder(current.right, array)
+      array << { key: current.key, value: current.value }
+    else
+      return array
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def height
-    raise NotImplementedError
+  # Time Complexity: O(n) - where n is equal to the number of TreeNodes in the tree
+  # Space Complexity: O(1) - constant
+  def height(current = @root)
+    if current
+      left_height = height(current.left)
+      right_height = height(current.right)
+
+      return (left_height > right_height ? left_height : right_height) + 1
+    else
+      return 0
+    end
   end
 
   # Optional Method
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity:
+  # Space Complexity:
   def bfs
-    raise NotImplementedError
   end
 
   # Useful for printing
diff --git a/test/tree_test.rb b/test/tree_test.rb
index 8811f14..b9ba069 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -1,10 +1,9 @@
-require_relative 'test_helper'
-
+require_relative "test_helper"
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
 describe Tree do
-  let (:tree) {Tree.new}
+  let (:tree) { Tree.new }
 
   let (:tree_with_nodes) {
     tree.add(5, "Peter")
@@ -37,23 +36,21 @@
     end
 
     it "will return the tree in order" do
-
-      expect(tree_with_nodes.inorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
-                                       {:key=>5, :value=>"Peter"}, {:key=>10, :value=>"Karla"}, 
-                                       {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+      expect(tree_with_nodes.inorder).must_equal [{ :key => 1, :value => "Mary" }, { :key => 3, :value => "Paul" },
+                                                  { :key => 5, :value => "Peter" }, { :key => 10, :value => "Karla" },
+                                                  { :key => 15, :value => "Ada" }, { :key => 25, :value => "Kari" }]
     end
   end
 
-
   describe "preorder" do
     it "will give an empty array for an empty tree" do
       expect(tree.preorder).must_equal []
     end
 
     it "will return the tree in preorder" do
-      expect(tree_with_nodes.preorder).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
-                                        {:key=>1, :value=>"Mary"}, {:key=>10, :value=>"Karla"}, 
-                                        {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+      expect(tree_with_nodes.preorder).must_equal [{ :key => 5, :value => "Peter" }, { :key => 3, :value => "Paul" },
+                                                   { :key => 1, :value => "Mary" }, { :key => 10, :value => "Karla" },
+                                                   { :key => 15, :value => "Ada" }, { :key => 25, :value => "Kari" }]
     end
   end
 
@@ -63,21 +60,32 @@
     end
 
     it "will return the tree in postorder" do
-      expect(tree_with_nodes.postorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
-                                         {:key=>25, :value=>"Kari"}, {:key=>15, :value=>"Ada"}, 
-                                         {:key=>10, :value=>"Karla"}, {:key=>5, :value=>"Peter"}]
+      expect(tree_with_nodes.postorder).must_equal [{ :key => 1, :value => "Mary" }, { :key => 3, :value => "Paul" },
+                                                    { :key => 25, :value => "Kari" }, { :key => 15, :value => "Ada" },
+                                                    { :key => 10, :value => "Karla" }, { :key => 5, :value => "Peter" }]
+    end
+  end
+
+  describe "height" do
+    it "will return 0 for an empty tree" do
+      expect(tree.height).must_equal 0
+    end
+    it "will return the height of the tree" do
+      expect(tree_with_nodes.height).must_equal 4
     end
   end
 
   describe "breadth first search" do
     it "will give an empty array for an empty tree" do
+      skip
       expect(tree.bfs).must_equal []
     end
 
     it "will return an array of a level-by-level output of the tree" do
-      expect(tree_with_nodes.bfs).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
-                                   {:key=>10, :value=>"Karla"}, {:key=>1, :value=>"Mary"}, 
-                                   {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+      skip
+      expect(tree_with_nodes.bfs).must_equal [{ :key => 5, :value => "Peter" }, { :key => 3, :value => "Paul" },
+                                              { :key => 10, :value => "Karla" }, { :key => 1, :value => "Mary" },
+                                              { :key => 15, :value => "Ada" }, { :key => 25, :value => "Kari" }]
     end
   end
-end
\ No newline at end of file
+end