From 1c6de75de50f1d8fa31eaa14fcbf165532f219e1 Mon Sep 17 00:00:00 2001
From: Kalkidan Ashenafi <kalkidanashenafi@gmail.com>
Date: Mon, 24 May 2021 09:00:59 -0700
Subject: [PATCH 1/2] methods finished, all tests passing

---
 lib/tree.rb | 102 ++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 91 insertions(+), 11 deletions(-)

diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..259e4c6 100644
--- a/lib/tree.rb
+++ b/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
@@ -18,45 +18,125 @@ def initialize
 
   # Time Complexity: 
   # Space Complexity: 
-  def add(key, value)
-    raise NotImplementedError
+  def add(key, value=nil)
+    new_node = TreeNode.new(key, value)
+
+    if @root.nil?
+      @root = new_node
+    else
+      add_helper(@root, new_node)
+    end
   end
 
+  def add_helper(curr_node, new_node)
+    return new_node if curr_node.nil?
+
+    if new_node.key <= curr_node.key
+      curr_node.left = add_helper(curr_node.left, new_node)
+    else
+      curr_node.right = add_helper(curr_node.right, new_node)
+    end
+
+    return curr_node
+  end  
+
   # Time Complexity: 
   # Space Complexity: 
   def find(key)
-    raise NotImplementedError
+    find_helper(@root, key)  #starts at root
   end
 
+  def find_helper(current, key)
+    return if current.nil?
+    if key == current.key
+      return current.value
+    elsif key < current.key
+      find_helper(current.left, key)
+    else 
+      find_helper(current.right, key)
+    end
+  end 
+
   # Time Complexity: 
   # Space Complexity: 
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
   end
+  
+  def inorder_helper(current, list)
+    return list if current.nil?
+    inorder_helper(current.left, list)
+    list << {key: current.key, value: current.value}
+    inorder_helper(current.right, list)
+    return list
+  end 
 
   # Time Complexity: 
   # Space Complexity: 
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
+  end
+
+  def preorder_helper(current, list)
+    return list if current.nil?
+    list << {key: current.key, value: current.value}
+    preorder_helper(current.left, list)
+    preorder_helper(current.right, list)
   end
 
   # Time Complexity: 
   # Space Complexity: 
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
+  end
+
+  def postorder_helper(current, list)
+    return list if current.nil?
+    postorder_helper(current.left, list)
+    postorder_helper(current.right, list)
+    list << {key: current.key, value: current.value}
   end
 
   # Time Complexity: 
   # Space Complexity: 
-  def height
-    raise NotImplementedError
+  def height(current = @root)
+    return 0 if current.nil?
+    return 1 if current.right.nil? && current.left.nil?
+
+    left_count = 0
+    right_count = 0
+    left_count += 1 + height(current.left)
+    right_count += 1 + height(current.right)
+    left_count > right_count ? left_count : right_count
+  end
+
+  def height_helper(node, side, count)
+    return count if node.nil?
+
+    count += 1
+    if side == 'left'
+      height_helper(node.left, 'left', count)
+    else
+      height_helper(node.right, 'right', count)
+    end
   end
 
   # Optional Method
   # Time Complexity: 
   # Space Complexity: 
   def bfs
-    raise NotImplementedError
+    return [] if @root.nil?
+    queue = []
+    list = []
+    queue.push(@root)
+    while queue.length > 0
+      current = queue[0]
+      list << {key: current.key, value: current.value}
+      queue.push(current.left) if current.left
+      queue.push(current.right) if current.right
+      queue.shift
+    end
+    return list 
   end
 
   # Useful for printing

From 8d733f566f67ce1a40a8d3899bf47296a677d0a9 Mon Sep 17 00:00:00 2001
From: Kalkidan Ashenafi <kalkidanashenafi@gmail.com>
Date: Wed, 2 Jun 2021 21:39:10 -0700
Subject: [PATCH 2/2] added s & t complexity

---
 lib/tree.rb | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/lib/tree.rb b/lib/tree.rb
index 259e4c6..61a5028 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,8 +16,8 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n) if balanced, otherwise O(n) where n is number of nodes
+  # Space Complexity: O(n), n is height
   def add(key, value=nil)
     new_node = TreeNode.new(key, value)
 
@@ -40,8 +40,8 @@ def add_helper(curr_node, new_node)
     return curr_node
   end  
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n) if balanced
+  # Space Complexity: O(n)
   def find(key)
     find_helper(@root, key)  #starts at root
   end
@@ -57,8 +57,8 @@ def find_helper(current, key)
     end
   end 
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n), n is number of nodes
+  # Space Complexity: O(n)
   def inorder
     return inorder_helper(@root, [])
   end
@@ -71,8 +71,8 @@ def inorder_helper(current, list)
     return list
   end 
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def preorder
     return preorder_helper(@root, [])
   end
@@ -84,8 +84,8 @@ def preorder_helper(current, list)
     preorder_helper(current.right, list)
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
   def postorder
     return postorder_helper(@root, [])
   end