Time - Sharon Cheung

lib/tree.rb

@@ -16,40 +16,128 @@ 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, key, value)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current, key, value)
+    return TreeNode.new(key,value) if current.nil?
+
+    if key < current.key 
+      current.left = add_helper(current.left,  key, value)
+    else
+      current.right = add_helper(current.right,  key, value)
+    end
+
+    return current
+  end
+
+  # Time Complexity: O(log n)
+  # Space Complexity: O(log n)
   def find(key)
-    raise NotImplementedError
+    return if @root.nil?
+
+    if @root == key
+      return @root.value
+    else
+      find_helper(@root, key)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(current, key)
+    return if current.nil?
+
+    if key < current.key
+      current.left = find_helper(current.left, key)
+    elsif key > current.key
+      current.right = find_helper(current.right, key)
+    else 
+      return current.value
+    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_node, list)
+    return list if current_node.nil?
+    # left 
+    inorder_helper(current_node.left, list)
+    # middle
+    list << {key: current_node.key, value: current_node.value}
+    # right
+    inorder_helper(current_node.right, list)
+
+    return list 
+  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_node, list)
+    return list if current_node.nil?
+    # middle
+    list << {key: current_node.key, value: current_node.value}
+    # left
+    preorder_helper(current_node.left, list)
+    #right
+    preorder_helper(current_node.right, list)
+
+    return list 
+  end
+
+  # Time Complexity:  O(n)
+  # Space Complexity:  O(n)
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
+  end
+
+  def postorder_helper(current_node, list)
+    return list if current_node.nil?
+    # left
+    postorder_helper(current_node.left, list)
+    #right
+    postorder_helper(current_node.right, list)
+    # middle
+    list << {key: current_node.key, value: current_node.value}
+
+    return list 
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def height
-    raise NotImplementedError
+    if @root.nil?
+      return 0 
+    else
+      height_helper(@root)
+    end
+  end
+
+  def height_helper(current)
+    return 0 if current.nil?
+    left = height_helper(current.left)
+    right = height_helper(current.right)
+
+    if (left > right)
+      return left + 1
+    else
+      return right + 1
+    end
   end
 
   # Optional Method