diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..3701173 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,122 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   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
+
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current, new_node)
+    if new_node.key <= current.key
+      if current.left.nil?
+        return current.left = new_node
+      else
+        add_helper(current.left, new_node)
+      end
+    else
+      if current.right.nil?
+        return current.right = new_node
+      else
+        add_helper(current.right, new_node)
+      end
+    end
+  end
+
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   def find(key)
-    raise NotImplementedError
+    return nil if @root.nil?
+    current = @root
+
+    while current != nil
+      if key == current.key
+        return current.value
+      elsif key < current.key
+        current = current.left
+      else
+        current = current.right
+      end
+    end
+
+    # if not found
+    return nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    # This method returns an array of all the elements in the tree, in order. (left, root, right)
+    inorder_array = []
+    inorder_helper(@root, inorder_array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current, array)
+    return array if current.nil?
+
+    inorder_helper(current.left, array)
+    array << { key: current.key, value: current.value }
+    inorder_helper(current.right, array)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    # This method returns an array of all the elements in a preorder fashion (root, left, right).
+    preorder_array = []
+
+    preorder_helper(@root, preorder_array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current, array)
+    return array if current.nil?
+
+    array << { key: current.key, value: current.value }
+    preorder_helper(current.left, array)
+    preorder_helper(current.right, array)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    # This method returns an array of all the elements in a postorder fashion (left, right, root).
+    postorder_array = []
+
+    postorder_helper(@root, postorder_array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current, array)
+    return array if current.nil?
+
+    postorder_helper(current.left, array)
+    postorder_helper(current.right, array)
+    array << { key: current.key, value: current.value }
+  end
+
+  # Time Complexity: O(n) - worst case for unbalanced, best case O(log n)
+  # Space Complexity: O(1)
   def height
-    raise NotImplementedError
+    # return 0 if @root == nil
+
+    height_helper(@root)
+  end
+
+  def height_helper(current, count = 0)
+    return count if current.nil?
+
+    
+    left_height = height_helper(current.left, count + 1)
+    right_height = height_helper(current.right, count + 1)
+    return [left_height, right_height].max
+
+    # return left_height > right_height ? left_height : right_height
   end
 
   # Optional Method