Leaves- Yitgop

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

@@ -2,12 +2,12 @@ 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
@@ -16,47 +16,129 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)/ O(n)
+  # Space Complexity: O(log n) for a balanced BST; O(n) for unbalanced BST
+  def add_helper(curr, key, value)
+    return TreeNode.new(key, value) if curr.nil?
+
+    if key < curr.key
+      curr.left = add_helper(curr.left, key, value)
+    else
+      curr.right = add_helper(curr.right, key, value)
+    end
+
+    return curr
+  end
+
   def add(key, value)
-    raise NotImplementedError
+    @root = add_helper(@root, key, value)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n)/O(n)
+  # Space Complexity: O(1)
   def find(key)
-    raise NotImplementedError
+    curr = @root
+
+    until curr.nil?
+      if key > curr.key
+        curr = curr.right
+      elsif key < curr.key
+        curr = curr.left
+      else
+        return curr.value
+      end
+    end
+
+    return nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def inorder_helper(curr, list)
+    return list if curr.nil?
+
+    # inorder: left - root - right 
+    inorder_helper(curr.left, list)
+    list << {key: curr.key, value: curr.value}
+    inorder_helper(curr.right, list)
+
+    return list
+  end
+
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def preorder_helper(curr, list) 
+    return list if curr.nil?
+
+    # preorder: root - left - right 
+    list << { key: curr.key, value: curr.value }
+    preorder_helper(curr.left, list)
+    preorder_helper(curr.right, list)
+
+    return list
+  end
+
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def postorder_helper(curr, list)
+    return list if curr.nil?
+
+    # postorder: left - right - root
+    postorder_helper(curr.left, list)
+    postorder_helper(curr.right, list)
+    list << { key: curr.key, value: curr.value }
+
+    return list
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(log n)/ O(n)
+  def height_helper(curr, height)
+    return height if curr.nil?
+
+    height += 1
+    left_height = height_helper(curr.left, height)
+    right_height = height_helper(curr.right, height)
+
+    return [left_height, right_height].max
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def height
-    raise NotImplementedError
+    return height_helper(@root, 0)
   end
 
   # Optional Method
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def bfs
-    raise NotImplementedError
+    visted = []
+    return visted if @root.nil?
+
+    to_visit = [@root]
+    until to_visit.empty?
+      curr = to_visit.shift
+      visted << {
+        key: curr.key,
+        value: curr.value
+      }
+
+      to_visit << curr.left if curr.left
+      to_visit << curr.right if curr.right
+    end
+
+    return visted
   end
 
   # Useful for printing

test/tree_test.rb

@@ -68,6 +68,16 @@
                                          {: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
@@ -80,4 +90,4 @@
                                    {:key=>15, :value=>"Ada"}, {:key=>25, :value=>"Kari"}]
     end
   end
-end
+end