Leaves - Alice

lib/tree.rb

@@ -1,64 +1,135 @@
 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
   attr_reader :root
   def initialize
     @root = nil
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+  
+  # Time Complexity: O(log n) for a balanced tree, O(n) for unbalanced
+  # Space Complexity: O(log n) for a balanced tree, O(n) for unbalanced
   def add(key, value)
-    raise NotImplementedError
+    if @root.nil?
+      @root = TreeNode.new(key, value)
+    else
+      add_helper(@root, key, value)
+    end
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+  def add_helper(current, key, value)
+    if current.nil?
+      return TreeNode.new(key, value)
+    else
+      if key < current.key
+        current.left = add_helper(current.left, key, value)
+      else
+        current.right = add_helper(current.right, key, value)
+      end
+    end
+    return current
+  end
+
+  # Time Complexity: O(log n) for a balanced tree, O(n) for unbalanced
+  # Space Complexity: O(log n) for a balanced tree, O(n) for unbalanced
   def find(key)
-    raise NotImplementedError
+    return nil if @root.nil?
+
+    find_helper(@root, key)
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+  def find_helper(current, key)
+    return nil if current.nil?
+
+    if key == current.key
+      return current.value
+    elsif key < current.key
+      find_helper(current.left, key)
+    else
+      find_helper(current.right, key)
+    end
+
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def inorder
-    raise NotImplementedError
+    inorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+  def inorder_helper(current, list)
+    return list if current.nil?
+
+    inorder_helper(current.left, list)
+    list << {key: current.key, value: current.value}
+    inorder_helper(current.right, list)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
-    raise NotImplementedError
+    preorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+  def preorder_helper(current, list)
+    return list if current.nil?
+
+    list << {key: current.key, value: current.value}
+    preorder_helper(current.left, list)
+    preorder_helper(current.right, list)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
-    raise NotImplementedError
+    postorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+  def postorder_helper(current, list)
+    return list if current.nil?
+
+    postorder_helper(current.left, list)
+    postorder_helper(current.right, list)
+    list << {key: current.key, value: current.value}
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def height
-    raise NotImplementedError
+    return 0 if @root.nil?
+
+    height_helper(@root, 0)
+  end
+
+  def height_helper(current, height)
+    return height if current.nil?
+
+    height +=1
+    left = height_helper(current.left, height)
+    right = height_helper(current.right, height)
+
+    if left > right
+      return left
+    else
+      return right
+    end
   end
-
   # Optional Method
   # Time Complexity: 
   # Space Complexity: 
   def bfs
     raise NotImplementedError
   end
-
+  
   # Useful for printing
   def to_s
     return "#{self.inorder}"