Nara

lib/tree.rb

@@ -16,42 +16,128 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n) for balanced trees, O(n) for unbalanced trees.
+  # Space Complexity: O(1)
   def add(key, value)
-    raise NotImplementedError
+    new_node = TreeNode.new(key, value)
+
+    if @root == nil
+      @root = new_node
+    else
+      current = @root 
+      add_helper(current, new_node)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current, new_node)
+    if current == nil 
+      return current = new_node
+    elsif 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) for balanced trees, O(n) for unbalanced trees.
+  # Space Complexity: O(1)
   def find(key)
-    raise NotImplementedError
+    return nil if @root == nil
+
+    current = @root
+    find_helper(current, key)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(current, key)
+    if current.key == key 
+      return current.value 
+    elsif key < current.key
+      current.left = find_helper(current.left, key)
+    else
+      current.right = find_helper(current.right, key)
+    end
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    array = []
+    return array if @root == nil
+    current = @root
+
+    return inorder_helper(current, array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current, array)
+    if current == nil
+       return array
+    else
+      inorder_helper(current.left, array)
+      array.push({:key => current.key, :value => current.value})
+      inorder_helper(current.right, array)
+    end
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    array = []
+    return array if @root == nil
+    current = @root
+
+    return preorder_helper(current, array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current, array)
+    if current == nil
+      return array
+    else
+      array.push({:key => current.key, :value => current.value})
+      preorder_helper(current.left, array)
+      preorder_helper(current.right, array)
+    end 
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    array = []
+    return array if @root == nil
+    current = @root
+
+    return postorder_helper(current, array)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current, array)
+    if current == nil
+      return array
+    else
+      postorder_helper(current.left, array)
+      postorder_helper(current.right, array)
+      array.push({:key => current.key, :value => current.value})
+    end 
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def height
-    raise NotImplementedError
+    return 0 if @root == nil
+    current = @root 
+    height_helper(current)
   end
 
+  def height_helper(current)
+    return 0 if current == nil
+    left_side = height_helper(current.left)
+    right_side = height_helper(current.right)
+
+    if left_side < right_side
+      return (right_side + 1)
+    else
+      return (left_side + 1)
+    end
+  end
   # Optional Method
   # Time Complexity: 
   # Space Complexity: