Angele Z

README.md

@@ -1,5 +1,7 @@
 # Tree Exercise
 
+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

lib/tree.rb

@@ -16,40 +16,105 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(logn) in worst case scenario
+  # Space Complexity: O(1) always just adding 1 new node
   def add(key, value)
-    raise NotImplementedError
+    @root = add_helper(@root, key, value)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def add_helper(current_node, key, value)
+    return TreeNode.new(key, value) if current_node.nil?
+
+    if key < current_node.key
+      current_node.left = add_helper(current_node.left, key, value)
+    else
+      current_node.right = add_helper(current_node.right, key, value)
+    end
+
+    return current_node
+  end
+
+  # Time Complexity: O(logn) since binary
+  # Space Complexity: O(1) since adding nothing new
   def find(key)
-    raise NotImplementedError
+    return find_helper(@root, key)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def find_helper(current_node, key)
+    return nil if current_node.nil?
+    return current_node.value if key == current_node.key
+
+    if key < current_node.key
+      find_helper(current_node.left, key)
+    else
+      find_helper(current_node.right, key)
+    end
+  end
+
+
+  # Time Complexity: O(n) since going to each node once, backtracking but still backtracking a smaller number of times than there are nodes, so it depends on the number of nodes no matter what.
+  # Space Complexity: O(1) - nothing being made
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # helper
+  def inorder_helper(current_node, list)
+    # left, root, right
+    return list if current_node.nil?
+    # recursion! left side first
+    inorder_helper(current_node.left, list)
+    list << {key: current_node.key, value: current_node.value}
+    inorder_helper(current_node.right, list)
+    return list
+  end
+
+  # Time Complexity: same as inorder
+  # Space Complexity: same as inorder
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def preorder_helper(current_node, list)
+    # root, left, right
+    return list if current_node.nil?
+    list << {key: current_node.key, value: current_node.value}
+    preorder_helper(current_node.left, list)
+    preorder_helper(current_node.right, list)
+    return list
+  end
+
+  # Time Complexity: same as inorder
+  # Space Complexity: same as inorder
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  def postorder_helper(current_node, list)
+    # left, right, root
+    return list if current_node.nil?
+    postorder_helper(current_node.left, list)
+    postorder_helper(current_node.right, list)
+    list << {key: current_node.key, value: current_node.value}
+    return list
+  end
+
+  # Time Complexity: O(n) since each node is visited once
+  # Space Complexity: O(1) since it doesn't make anything new
   def height
-    raise NotImplementedError
+    return height_helper(@root, 0)
+  end
+
+  def height_helper(current_node, current_height)
+    return 0 if current_node.nil?
+    left_height = height_helper(current_node.left, current_height)
+    right_height = height_helper(current_node.right, current_height)
+    if left_height > right_height
+      return left_height + 1
+    else
+      return right_height + 1
+    end
+
   end
 
   # Optional Method

test/tree_test.rb

@@ -5,6 +5,8 @@
 
 describe Tree do
   let (:tree) {Tree.new}
+  let (:tree2) {Tree.new}
+  let (:tree3) {Tree.new}
 
   let (:tree_with_nodes) {
     tree.add(5, "Peter")
@@ -16,6 +18,29 @@
     tree
   }
 
+  let (:tree_with_nodes2) {
+    tree2.add(5, "Peter")
+    tree2.add(3, "Paul")
+    tree2.add(1, "Mary")
+    tree2.add(10, "Karla")
+    tree2.add(15, "Ada")
+    tree2.add(25, "Kari")
+    tree2.add(13, "Karino")
+    tree2
+  }
+
+  let (:tree_with_nodes3) {
+    tree3.add(5, "Peter")
+    tree3.add(3, "Paul")
+    tree3.add(1, "Mary")
+    tree3.add(10, "Karla")
+    tree3.add(15, "Ada")
+    tree3.add(25, "Kari")
+    tree3.add(17, "Karino")
+    tree3.add(30, "Karenina")
+    tree3
+  }
+
   it "add & find values" do
     tree.add(5, "Peter")
     expect(tree.find(5)).must_equal "Peter"
@@ -68,6 +93,24 @@
                                          {:key=>10, :value=>"Karla"}, {:key=>5, :value=>"Peter"}]
     end
   end
+
+  describe "height" do
+    it "returns 0 for an empty tree" do
+      expect(tree.height).must_equal 0
+    end
+
+    it "returns correct height of tree" do
+      expect(tree_with_nodes.height).must_equal 4
+    end
+
+    it "returns correct height of 2nd tree" do
+      expect(tree_with_nodes2.height).must_equal 4
+    end
+
+    it "returns correct height of 3rd tree" do
+      expect(tree_with_nodes3.height).must_equal 5
+    end
+  end
 
   describe "breadth first search" do
     it "will give an empty array for an empty tree" do
@@ -80,4 +123,4 @@
                                    {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
     end
   end
-end
+end