Time - Yesenia

lib/tree.rb

@@ -16,42 +16,127 @@ 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)
+    return new_node if current.nil? # base case
+
+    if new_node.key <= current.key
+      current.left = add_helper(current.left, new_node)
+    else 
+      current.right = add_helper(current.right, new_node)
+    end 
+
+    return current 
+  end 
+
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   def find(key)
-    raise NotImplementedError
+    current = @root 
+    return nil if current.nil? 
+    return current.value if key == current.key 
+
+    until current.nil?
+      if key == current.key 
+        return current.value
+      elsif key  < current.key 
+        current = current.left 
+      elsif key > current.key 
+        current = current.right
+      end 
+    end 
+
+    return nil # case when key not found
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    root = @root
+    list = []
+
+    inorder_helper(root, list)
+
+    return list
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current_node, list)
+    return if current_node.nil?
+
+    inorder_helper(current_node.left, list)
+    list << {:key => current_node.key, :value => current_node.value}
+    inorder_helper(current_node.right, list)
+  end 
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    root = @root
+    list = []
+
+    preorder_helper(root, list)
+
+    return list
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current_node, list)
+    return if current_node.nil?
+
+    list << {:key => current_node.key, :value => current_node.value}
+    preorder_helper(current_node.left, list)
+    preorder_helper(current_node.right, list)
+  end 
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    root = @root
+    list = []
+
+    postorder_helper(root, list)
+
+    return list
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current_node, list)
+    return if current_node.nil?
+
+    postorder_helper(current_node.left, list)
+    postorder_helper(current_node.right, list)
+    list << {:key => current_node.key, :value => current_node.value}
+  end 
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(log n) - balanced 
   def height
-    raise NotImplementedError
+    current = @root 
+    return height_helper(current, 0)
   end
 
+  def height_helper(current_node, height_count)
+    return 0 if current_node.nil? 
+
+    left_size = height_helper(current_node.left, height_count+1)
+    right_size = height_helper(current_node.right, height_count+1)
+
+    if left_size >= right_size
+      return left_size + 1 
+    else 
+      return right_size + 1
+    end 
+  end 
+
   # Optional Method
   # Time Complexity: 
   # Space Complexity: