diff --git a/binary_search_tree/tree.py b/binary_search_tree/tree.py
index cdd5abc..b568ab7 100644
--- a/binary_search_tree/tree.py
+++ b/binary_search_tree/tree.py
@@ -14,44 +14,119 @@ class Tree:
     def __init__(self):
         self.root = None
 
-    # Time Complexity: 
-    # Space Complexity: 
+    # Time Complexity: O(log N) or O(n)
+    # Space Complexity: O(n)
+
+    def insert_node_helper(self, current_node, key, value):
+        if current_node == None:
+            return TreeNode(key, value)
+
+        if key < current_node.key:
+            current_node.left = self.insert_node_helper(current_node.left, key, value)
+        else:
+            current_node.right = self.insert_node_helper(current_node.right, key, value)
+        return current_node
+
     def add(self, key, value = None):
-        pass
+        # BST is empty
+        if self.root is None:
+            self.root = TreeNode(key, value)
 
-    # Time Complexity: 
-    # Space Complexity: 
+        # BST is not empty
+        self.insert_node_helper(self.root, key, value)
+        
+
+    # Time Complexity: O(log N) or O(n)
+    # Space Complexity: O(n) 
     def find(self, key):
-        pass
+        if self.root == None:
+            return None
+        current = self.root
+        while current != None:
+            if current.key == key:
+                return current.value
+            elif current.key < key:
+                current = current.right
+            else:
+                current = current.left
+        return None
+
 
-    # Time Complexity: 
-    # Space Complexity: 
+    # Time Complexity: O(n)
+    # Space Complexity: O(n)
+    def inorder_helper(self, current, result):
+        if current is None:
+            return result
+        else:
+            self.inorder_helper(current.left, result)
+            result.append({'key': current.key, 'value': current.value})
+            self.inorder_helper(current.right, result)
+            return result
+            
     def inorder(self):
-        pass
+        result = []
+        # result_value = self.inorder_helper(self.root, result)
+        return self.inorder_helper(self.root, result)        
 
-    # Time Complexity: 
-    # Space Complexity:     
+    # Time Complexity: O(n)
+    # Space Complexity: O(n)
+    def preorder_helper(self, current, result):
+        if current:
+            result.append({"key": current.key, "value": current.value}) 
+            self.preorder_helper(current.left, result)
+            self.preorder_helper(current.right, result) 
+        return result
     def preorder(self):
-        pass
+        result = []
+        # self.preorder_helper(self.root, result)
+        return self.preorder_helper(self.root, result)
 
-    # Time Complexity: 
-    # Space Complexity:     
+
+    # Time Complexity: O(n)
+    # Space Complexity: O(n)
+    def postorder_helper(self, current, result):
+        if current:
+            self.postorder_helper(current.left, result)
+            self.postorder_helper(current.right, result)
+            result.append({"key": current.key, "value": current.value})     
     def postorder(self):
-        pass
+        result = []
+        self.postorder_helper(self.root, result)
+        return result
 
-    # Time Complexity: 
-    # Space Complexity:     
+    # Time Complexity: O(n)
+    # Space Complexity: O(1)
+    def height_helper(self, current):
+        if current == None:
+            return 0
+        if current:
+            height_left = self.height_helper(current.left)
+            height_right = self.height_helper(current.right)
+            return max(height_left, height_right)+1    
     def height(self):
-        pass
+        
+        return self.height_helper(self.root)
 
 
 #   # Optional Method
-#   # Time Complexity: 
-#   # Space Complexity: 
+#   # Time Complexity: O(n)
+#   # Space Complexity: O(n)
+
     def bfs(self):
-        pass
+        result = []
 
-        
+        if self.root == None:
+            return result
+
+        queue = [self.root]
+        while queue:
+            current = queue.pop(0)
+            result.append({"key": current.key, "value": current.value})
+            if current.left:
+                queue.append(current.left)
+            if current.right:
+                queue.append(current.right)
+        return result
 
 
 #   # Useful for printing