water - mackenzie

lib/tree.rb

@@ -2,12 +2,12 @@ class TreeNode
   attr_reader :key, :value
   attr_accessor :left, :right
 
-   def initialize(key, val)
+  def initialize(key, val)
     @key = key
     @value = val
     @left = nil
     @right = nil
-   end
+  end
 end
 
 class Tree
@@ -16,42 +16,108 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
-  def add(key, value)
-    raise NotImplementedError
+  # Time Complexity: O(log n) if balanced, up to O(n) if unbalanced
+  # Space Complexity: O(log n) if balanced, up to O(n) if unbalanced
+  def add(key, value = nil)
+    if @root.nil?
+      @root = TreeNode.new(key,value)
+    else
+      add_helper(@root, key, value)
+    end
+
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current_node, key, value)
+    if current_node.nil? 
+      current_node = TreeNode.new(key, value)
+    elsif key <= current_node.key 
+      current_node.left = add_helper(current_node.left, key, value)
+    else
+      current_node.right = add_helper(current_node.right, key, value)
+    end
+
+    return current_node
+  end
+
+
+  # Time Complexity: O(log n) if balanced, up to O(n) if unbalanced
+  # Space Complexity: O(log n) if balanced, up to O(n) if unbalanced
   def find(key)
-    raise NotImplementedError
+    if @root.nil?
+      return nil
+    else
+      find_helper(@root, key)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(current_node, key)
+    if current_node.nil? 
+      return nil
+    elsif current_node.key == key
+      return current_node.value
+    elsif key < current_node.key
+      find_helper(current_node.left, key)
+    else
+      find_helper(current_node.right, key)
+    end
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current, values)
+    return values if current.nil?
+
+    inorder_helper(current.left, values)
+    values << {key: current.key, value: current.value}
+    inorder_helper(current.right, values)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current, values)
+    return values if current.nil?
+
+    values << {key: current.key, value: current.value}
+    preorder_helper(current.left, values)
+    preorder_helper(current.right, values)
+  end
+
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current, values)
+    return values if current.nil?
+
+    postorder_helper(current.left, values)
+    postorder_helper(current.right, values)
+    values << {key: current.key, value: current.value}
+  end 
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def height
-    raise NotImplementedError
+    return height_helper(@root)
   end
 
+  def height_helper(current)
+    return 0 if current.nil?
+
+    return 1 + [height_helper(current.left), height_helper(current.right)].max
+  end
+
+
   # Optional Method
   # Time Complexity: 
   # Space Complexity: 

test/tree_test.rb

@@ -96,7 +96,7 @@
     end
 
     it "will report the height for a balanced tree" do
-      expect(tree_with_nodes.height).must_equal 3
+      expect(tree_with_nodes.height).must_equal 4
     end
 
     it "will report the height for unbalanced trees" do