diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..9e493ba 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,45 +16,127 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(logn) if the tree is balanced (best case), O(n) if tree is unbalanced (worst case)
+  # Space Complexity: O(1)
   def add(key, value)
-    raise NotImplementedError
+    if !@root
+      new_node = TreeNode.new(key, value)
+      @root = new_node
+      return
+    end
+
+    current = @root
+    new_node = TreeNode.new(key, value)
+
+    until !current
+      if new_node.key <= current.key # GO LEFT
+        if !current.left
+          current.left = new_node
+          return
+        else
+          current = current.left
+        end
+      else # new_node.value > current.value # GO RIGHT
+        if !current.right
+          current.right = new_node
+          return
+        else
+        current = current.right
+        end
+      end
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(logn) where n is the length of the array if the tree is balanced. O(n) if not.
+  # Space Complexity: O(1)
   def find(key)
-    raise NotImplementedError
+    return nil if !@root
+    current = @root
+
+    until current == nil
+      return current.value if key == current.key
+      key < current.key ? current = current.left : current = current.right
+    end
+
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n-squared) 
+  # Space Complexity: O(n) where n is the height of the recursion stack
   def inorder
-    raise NotImplementedError
+    @output = []
+    current = @root
+
+    return @output if !@root
+
+    def analyzeInorder(current)
+      analyzeInorder(current.left) if current.left
+      @output << {:key => current.key, :value => current.value}
+      analyzeInorder(current.right) if current.right
+    end
+    
+    analyzeInorder(current)
+  
+    return @output
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n-squared) 
+  # Space Complexity: O(n) where n is the height of the recursion stack
   def preorder
-    raise NotImplementedError
+    @output = []
+    current = @root
+
+    return @output if !@root
+
+    def analyzePreorder(current)
+      @output << {:key => current.key, :value => current.value}
+      analyzePreorder(current.left) if current.left
+      analyzePreorder(current.right) if current.right
+    end
+    
+    analyzePreorder(current)
+  
+    return @output
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n-squared) 
+  # Space Complexity: O(n) where n is the height of the recursion stack
   def postorder
-    raise NotImplementedError
+    @output = []
+    current = @root
+
+    return @output if !@root
+
+    def analyzePostorder(current)
+      analyzePostorder(current.left) if current.left
+      analyzePostorder(current.right) if current.right
+      @output << {:key => current.key, :value => current.value}
+    end
+    
+    analyzePostorder(current)
+  
+    return @output
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n) if tree is balanced, O(n) if unbalanced
+  # Space Complexity: O(1)
   def height
-    raise NotImplementedError
+    return 0 if !@root
+
+    def findMaxHeight(node)
+      return 0 if !node
+
+      height_left = findMaxHeight(node.left)
+      height_right = findMaxHeight(node.right)
+      
+      return height_left > height_right ? (height_left + 1) : (height_right + 1)
+    end
+    
+    findMaxHeight(@root)
   end
 
   # Optional Method
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity:
+  # Space Complexity:
   def bfs
     raise NotImplementedError
   end
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..48e341a
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,3 @@
+{
+  "lockfileVersion": 1
+}
diff --git a/test/tree_test.rb b/test/tree_test.rb
index 8811f14..07c8c3e 100644
--- a/test/tree_test.rb
+++ b/test/tree_test.rb
@@ -1,6 +1,7 @@
+require 'minitest/autorun'
+require 'minitest/skip_dsl'
 require_relative 'test_helper'
 
-
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
 describe Tree do
@@ -10,7 +11,9 @@
     tree.add(5, "Peter")
     tree.add(3, "Paul")
     tree.add(1, "Mary")
+    # tree.add(4, "Elle")
     tree.add(10, "Karla")
+    # tree.add(9, "Brad")
     tree.add(15, "Ada")
     tree.add(25, "Kari")
     tree
@@ -38,8 +41,8 @@
 
     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"}, 
+      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
@@ -51,8 +54,8 @@
     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"}, 
+      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 +66,31 @@
     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"}, 
+      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 "breadth first search" do
+  describe "height" do
+    it "returns 0 for an empty tree" do
+      expect(tree.height).must_equal 0
+    end
+
+    it "returns correct height of tree" do
+      expect(tree_with_nodes.height).must_equal 4
+    end
+  end
+
+  xdescribe "breadth first search" do # optional
     it "will give an empty array for an empty tree" do
       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"}, 
+      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