diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..7cf01da 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,87 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)
+  # Space Complexity: O(n) - call stack
   def add(key, value)
-    raise NotImplementedError
+    if @root.nil?
+      @root = TreeNode.new(key, value)
+      return true
+    end
+
+    add_helper(key, value, @root)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def find(key)
-    raise NotImplementedError
+  def add_helper(key, value, current)
+    return TreeNode.new(key, value) if current.nil?
+
+    if key < current.key
+      current.left = add_helper(key, value, current.left)
+    else
+      current.right = add_helper(key, value, current.right)
+    end
+
+    return current
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def inorder
-    raise NotImplementedError
+  # Time Complexity: O(log n)
+  # Space Complexity: O(n) - call stack
+  def find(key, current = @root)
+    return nil if current.nil?
+    return current.value if current.key == key
+
+    if key < current.key
+      return find(key, current.left)
+    else
+      return find(key, current.right)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def preorder
-    raise NotImplementedError
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def inorder(current = @root, answer = [])
+
+    if current
+      inorder(current.left, answer)
+      answer.push({key: current.key, value: current.value})
+      inorder(current.right, answer)
+    end
+
+    return answer
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def postorder
-    raise NotImplementedError
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def preorder(current = @root, answer = [])
+    if current
+      answer.push({key: current.key, value: current.value})
+      preorder(current.left, answer)
+      preorder(current.right, answer)
+    end
+
+    return answer
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def height
-    raise NotImplementedError
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def postorder(current = @root, answer = [])
+    if current
+      postorder(current.left, answer)
+      postorder(current.right, answer)
+      answer.push({key: current.key, value: current.value})
+    end
+
+    return answer
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def height(current = @root)
+    unless current
+      return 0
+    end
+
+    return 1 + [height(current.left), height(current.right)].max
   end
 
   # Optional Method
@@ -63,4 +110,4 @@ def bfs
   def to_s
     return "#{self.inorder}"
   end
-end
+end
\ No newline at end of file
diff --git a/test/tree_test.rb b/test/tree_test.rb
index 60f5981..801f9ee 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -51,7 +51,7 @@
     end
 
     it "will return the tree in preorder" do
-      expect(tree_with_nodes.preorder).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
+      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
@@ -91,7 +91,7 @@
     it "will return 1 for a tree of height 1" do
       my_tree = Tree.new
 
-      my_tree.add(100)
+      my_tree.add(100, 100)
       expect(my_tree.height).must_equal 1
     end
 
@@ -102,11 +102,11 @@
     it "will report the height for unbalanced trees" do
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(110)
-      my_tree.add(120)
-      my_tree.add(130)
-      my_tree.add(140)
+      my_tree.add(100, 100)
+      my_tree.add(110, 110)
+      my_tree.add(120, 120)
+      my_tree.add(130, 130)
+      my_tree.add(140, 140)
 
       expect(my_tree.height).must_equal 5
 
@@ -114,11 +114,11 @@
 
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(90)
-      my_tree.add(80)
-      my_tree.add(70)
-      my_tree.add(60)
+      my_tree.add(100, 100)
+      my_tree.add(90, 90)
+      my_tree.add(80, 80)
+      my_tree.add(70, 70)
+      my_tree.add(60, 60)
 
       expect(my_tree.height).must_equal 5
     end