Leaves_Ga-Young

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

@@ -1,64 +1,170 @@
 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: 
+
+  # a recursive helper method for adding a node to a binary search tree
+  # 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
+  # end
+
+  # Time Complexity: O(log n) where n is number of nodes ?
+  # Space Complexity: O(n) where n is number of nodes ?
   def add(key, value)
-    raise NotImplementedError
+
+    if @root.nil?
+      @root = TreeNode.new(key, value)
+    else
+      current = @root
+
+      while true
+
+        if key <= current.key
+
+          if !current.left.nil?
+            current = current.left
+          else
+            current.left = TreeNode.new(key, value)
+            return
+          end
+
+        else
+
+          if !current.right.nil?
+            current = current.right
+          else
+            current.right = TreeNode.new(key, value)
+            return
+          end
+        end 
+      end
+    end
+
+    # if using the recursive helper method instead
+    # @root = add_helper(@root, key, value)
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+  
+  # Time Complexity: O(log n) where n is number of nodes ?
+  # Space Complexity: O(1) or is this N/A?
   def find(key)
-    raise NotImplementedError
+    if @root.nil?
+      return nil
+    else
+      current = @root
+      while true
+        if key == current.key
+          return current.value
+        elsif key < current.key
+          current = current.left
+        else 
+          current = current.right
+        end
+      end
+    end
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+
+  def inorder_helper(current_node, list)
+    return list if current_node.nil?
+
+    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: O(n) where n is number of nodes
+  # Space Complexity: O(n) where n is number of nodes
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+
+  def preorder_helper(current_node, list)
+    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)
+  end
+
+  # Time Complexity: O(n) where n is number of nodes
+  # Space Complexity: O(n) where n is number of nodes 
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+
+  def postorder_helper(current_node, list)
+    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 }
+  end
+
+  # Time Complexity: O(n) where n is number of nodes
+  # Space Complexity: O(n) where n is number of nodes 
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
   end
-
-  # Time Complexity: 
-  # Space Complexity: 
+
+
+
+  def height_helper(current)
+    return 0 if current.nil?
+
+    left_height = height_helper(current.left)
+    right_height = height_helper(current.right)
+
+    return [left_height, right_height].max + 1
+  end
+
+  # Time Complexity: O(n) where n is number of nodes
+  # Space Complexity: O(1)
   def height
-    raise NotImplementedError
+    return height_helper(@root)
   end
-
+  
   # Optional Method
   # Time Complexity: 
   # Space Complexity: 
   def bfs
     raise NotImplementedError
+
+    # list = []
+    # return list if @root.nil?
+    # queue = [@root]
+
+    # until queue.empty
+    #   current = queue.shift
+    #   queue.push(current.left) unless current.left.nil?
+    #   queue.push(current.right) unless current.right.nil?
+
+    #   list << { key: current.key, value: current.value }
+    # end
   end
-
+  
   # Useful for printing
   def to_s
     return "#{self.inorder}"

test/tree_test.rb

@@ -5,7 +5,7 @@
 
 describe Tree do
   let (:tree) {Tree.new}
-
+  
   let (:tree_with_nodes) {
     tree.add(5, "Peter")
     tree.add(3, "Paul")
@@ -15,69 +15,80 @@
     tree.add(25, "Kari")
     tree
   }
-
+  
   it "add & find values" do
     tree.add(5, "Peter")
     expect(tree.find(5)).must_equal "Peter"
-
+    
     tree.add(15, "Ada")
     expect(tree.find(15)).must_equal "Ada"
-
+    
     tree.add(3, "Paul")
     expect(tree.find(3)).must_equal "Paul"
   end
-
+  
   it "can't find anything when the tree is empty" do
     expect(tree.find(50)).must_be_nil
   end
-
+  
   describe "inorder" do
     it "will give an empty array for an empty tree" do
       expect(tree.inorder).must_equal []
     end
-
+    
     it "will return the tree in order" do
-
+      
       expect(tree_with_nodes.inorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
-                                       {:key=>5, :value=>"Peter"}, {:key=>10, :value=>"Karla"}, 
-                                       {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
-    end
-  end
-
-
-  describe "preorder" do
-    it "will give an empty array for an empty tree" do
-      expect(tree.preorder).must_equal []
-    end
-
-    it "will return the tree in preorder" do
-      expect(tree_with_nodes.preorder).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
-                                        {:key=>1, :value=>"Mary"}, {:key=>10, :value=>"Karla"}, 
-                                        {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
-    end
-  end
-
-  describe "postorder" do
-    it "will give an empty array for an empty tree" do
-      expect(tree.postorder).must_equal []
-    end
-
-    it "will return the tree in postorder" do
-      expect(tree_with_nodes.postorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
-                                         {:key=>25, :value=>"Kari"}, {:key=>15, :value=>"Ada"}, 
-                                         {:key=>10, :value=>"Karla"}, {:key=>5, :value=>"Peter"}]
+        {:key=>5, :value=>"Peter"}, {:key=>10, :value=>"Karla"}, 
+        {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+      end
     end
-  end
-
-  describe "breadth first search" do
-    it "will give an empty array for an empty tree" do
-      expect(tree.bfs).must_equal []
-    end
-
-    it "will return an array of a level-by-level output of the tree" do
-      expect(tree_with_nodes.bfs).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
-                                   {:key=>10, :value=>"Karla"}, {:key=>1, :value=>"Mary"}, 
-                                   {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
-    end
-  end
-end
+
+
+    describe "preorder" do
+      it "will give an empty array for an empty tree" do
+        expect(tree.preorder).must_equal []
+      end
+
+      it "will return the tree in preorder" do
+        expect(tree_with_nodes.preorder).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
+          {:key=>1, :value=>"Mary"}, {:key=>10, :value=>"Karla"}, 
+          {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+        end
+      end
+
+      describe "postorder" do
+        it "will give an empty array for an empty tree" do
+          expect(tree.postorder).must_equal []
+        end
+
+        it "will return the tree in postorder" do
+          expect(tree_with_nodes.postorder).must_equal [{:key=>1, :value=>"Mary"}, {:key=>3, :value=>"Paul"}, 
+            {:key=>25, :value=>"Kari"}, {:key=>15, :value=>"Ada"}, 
+            {: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
+        end
+
+        # describe "breadth first search" do
+        #   it "will give an empty array for an empty tree" do
+        #     expect(tree.bfs).must_equal []
+        #   end
+
+        #   it "will return an array of a level-by-level output of the tree" do
+        #     expect(tree_with_nodes.bfs).must_equal [{:key=>5, :value=>"Peter"}, {:key=>3, :value=>"Paul"}, 
+        #       {:key=>10, :value=>"Karla"}, {:key=>1, :value=>"Mary"}, 
+        #       {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
+        #     end
+        #   end
+      end
+