Sockets - Erica

README.md

@@ -5,7 +5,7 @@ This project is due **Monday September 2nd, 2019**
 In this exercise you will implement, in Ruby, several Tree methods.
 
 - `add(value)` - This method adds a value to the Binary Search Tree
-- `find(value)` - This method returns true if the given value is in the tree and false otherwise.
+- `find(value)` - This method returns the corresponding value if the given key is in the tree and nil otherwise.  
 - `inorder` - This method returns an array of all the elements in the tree, in order.
 - `postorder` - This method returns an array of all the elements in a postorder fashion (left, right , root).
 - `preorder` - This method returns an array of all the elements in a preorder fashion (root, left, right).

lib/tree.rb

@@ -16,40 +16,79 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n) (O(logn) if tree is balanced), where n is the height of the tree
+  # Space Complexity: O(1)
   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: 
+  # Time Complexity: O(n) (O(logn) if tree is balanced), where n is the height of the tree
+  # Space Complexity: O(1)
   def find(key)
-    raise NotImplementedError
+    return nil if @root == nil
+
+    current = @root
+
+    until current == nil
+      if key == current.key
+        return current.value
+      elsif key < current.key
+        current = current.left
+      else
+        current = current.right
+      end
+    end
+
+    return nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n), where n is the number of nodes
+  # Space Complexity: O(n), where n is the number of nodes
   def inorder
-    raise NotImplementedError
+    return [] if @root == nil
+
+    current = @root 
+    tree = []
+
+    return inorder_helper(current, tree)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n), where n is the number of nodes
+  # Space Complexity: O(n), where n is the number of nodes
   def preorder
-    raise NotImplementedError
+    return [] if @root == nil
+
+    current = @root 
+    tree = []
+
+    return preorder_helper(current, tree)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n), where n is the number of nodes
+  # Space Complexity: O(n), where n is the number of nodes
   def postorder
-    raise NotImplementedError
+    return [] if @root == nil
+
+    current = @root 
+    tree = []
+
+    return postorder_helper(current, tree)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n), where n is the number of nodes
+  # Space Complexity: O(1)
   def height
-    raise NotImplementedError
+    return 0 if @root == nil
+
+    current = @root
+
+    return height_helper(current, 1, 1)
   end
 
   # Optional Method
@@ -63,4 +102,56 @@ def bfs
   def to_s
     return "#{self.inorder}"
   end
+
+  private
+
+  def add_helper(current, new_node)
+    return new_node if current == nil
+
+    if current.key >= new_node.key
+      current.left = add_helper(current.left, new_node)
+    else
+      current.right = add_helper(current.right, new_node)
+    end
+
+    return current
+  end
+
+  def inorder_helper(current, tree)
+    return tree if current == nil
+
+    inorder_helper(current.left, tree)
+    tree.push({ :key => current.key, :value => current.value })
+    inorder_helper(current.right, tree)
+
+  end
+
+  def preorder_helper(current, tree)
+    return tree if current == nil
+
+    tree.push({ :key => current.key, :value => current.value })
+
+    preorder_helper(current.left, tree)
+    preorder_helper(current.right, tree)
+  end
+
+  def postorder_helper(current, tree)
+    return tree if current == nil
+
+    postorder_helper(current.left, tree)
+    postorder_helper(current.right, tree)
+
+    tree.push({ :key => current.key, :value => current.value })
+  end
+
+  def height_helper(current, current_height, max_height)
+    return max_height if current == nil
+
+    max_height = current_height if current_height > max_height
+
+    max_height = height_helper(current.left, current_height + 1, max_height)
+    max_height = height_helper(current.right, current_height +1, max_height)
+
+    return max_height
+  end
 end