Water - Jessica

lib/tree.rb

@@ -1,13 +1,15 @@
+#All Big O is assumed balanced tree
+
 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
@@ -16,40 +18,97 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)
+  # Space Complexity: Olog (n) 
   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: 
+  def add_helper(current, new_node)
+    return new_node if current.nil?
+
+    if 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)
+  # Space Complexity: O(log n)
   def find(key)
-    raise NotImplementedError
+    return find_helper(@root, key)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(current, key)
+    return nil if current.nil?
+    if current.key == 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
+    return inorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def inorder_helper(current, nodes)
+    return nodes if current.nil?
+    inorder_helper(current.left, nodes)
+    nodes << {key: current.key, value: current.value}
+    inorder_helper(current.right, nodes)
+  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, nodes)
+    return nodes if current.nil?
+    nodes << {key: current.key, value: current.value}
+    preorder_helper(current.left, nodes)
+    preorder_helper(current.right, nodes)
+  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, nodes)
+    return nodes if current.nil?
+    postorder_helper(current.left, nodes)
+    postorder_helper(current.right, nodes)
+    nodes << {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?
+    left = height_helper(current.left)
+    right = height_helper(current.right)
+    return 1 + [left,right].max
   end
 
   # Optional Method

test/tree_test.rb

@@ -91,7 +91,7 @@
     it "will return 1 for a tree of height 1" do
       my_tree = Tree.new
 
-      my_tree.add(100)
+      my_tree.add(100, 100)
       expect(my_tree.height).must_equal 1
     end
 
@@ -102,23 +102,23 @@
     it "will report the height for unbalanced trees" do
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(110)
-      my_tree.add(120)
-      my_tree.add(130)
-      my_tree.add(140)
+      my_tree.add(100, 100)
+      my_tree.add(110, 110)
+      my_tree.add(120, 120)
+      my_tree.add(130, 130)
+      my_tree.add(140, 140)
 
       expect(my_tree.height).must_equal 5
 
       my_tree = Tree.new
 
       my_tree = Tree.new
 
-      my_tree.add(100)
-      my_tree.add(90)
-      my_tree.add(80)
-      my_tree.add(70)
-      my_tree.add(60)
+      my_tree.add(100, 100)
+      my_tree.add(90, 90)
+      my_tree.add(80, 80)
+      my_tree.add(70, 70)
+      my_tree.add(60, 60)
 
       expect(my_tree.height).must_equal 5
     end