From 97d733ec8d33beef272c61809d003c6c0ca4a64c Mon Sep 17 00:00:00 2001
From: Lola Llanes <mslourdesllanes@gmail.com>
Date: Mon, 4 Jan 2021 22:48:01 -0800
Subject: [PATCH] answered tree search exercises

---
 lib/tree.rb | 121 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 103 insertions(+), 18 deletions(-)

diff --git a/lib/tree.rb b/lib/tree.rb
index c0d4b51..8ef529b 100644
--- a/lib/tree.rb
+++ b/lib/tree.rb
@@ -16,40 +16,125 @@ def initialize
     @root = nil
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(log n) 
+  # Space Complexity: O(log n)
+  def add_helper(current_node, key, value)
+    if current_node.nil?
+      return TreeNode.new(key, value) 
+    end
+
+    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
+
   def add(key, value)
-    raise NotImplementedError
+    @root = add_helper(@root, key, value)
+  end
+
+  # Time Complexity: O(logn)
+  # Space Complexity: O(logn)
+  def find_helper(current_node, target)
+    if current_node == nil
+      return current_node 
+    end
+
+    if current_node.key == target
+      return current_node.value
+    end
+
+    if target < current_node.key
+      find_helper(current_node.left, target)
+    else
+      find_helper(current_node.right, target)
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def find(key)
-    raise NotImplementedError
+    return find_helper(@root, key)
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def inorder_helper(current_node, list)
+    if current_node.nil?
+      return list 
+    end
+
+    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: 
-  # Space Complexity: 
   def inorder
-    raise NotImplementedError
+    return inorder_helper(@root, [])
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def preorder_helper(current_node, list)
+    if current_node.nil?
+      return list 
+    end
+
+    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: 
-  # Space Complexity: 
   def preorder
-    raise NotImplementedError
+    return preorder_helper(@root, [])
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def postorder_helper(current_node, list)
+    if current_node.nil?
+      return list 
+    end
+    
+    postorder_helper(current_node.left, list)
+    postorder_helper(current_node.right, list)
+    list << {key: current_node.key, value: current_node.value}
+    
+    return list
+  end
+  
   def postorder
-    raise NotImplementedError
+    return postorder_helper(@root, [])
+  end
+
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def height_helper(current_node)
+    if current_node.nil?
+      return 0 
+    end
+
+    left = height_helper(current_node.left)
+    right = height_helper(current_node.right)
+    
+    if left > right
+      return left += 1
+    else
+      return right += 1
+    end
   end
 
-  # Time Complexity: 
-  # Space Complexity: 
   def height
-    raise NotImplementedError
+    if @root.nil?
+      return 0 
+    end
+  
+    return height_helper(@root)
   end
 
   # Optional Method