From 03157749e07fbbd68b3e5ea6b57ebd354aae6f8f Mon Sep 17 00:00:00 2001
From: Wenjie <traxiaojie@gmail.com>
Date: Thu, 17 May 2018 20:18:18 -0700
Subject: [PATCH] Finished recursion homework

---
 mystery-methods.rb | 48 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/mystery-methods.rb b/mystery-methods.rb
index 2caa835..2eb27aa 100644
--- a/mystery-methods.rb
+++ b/mystery-methods.rb
@@ -7,6 +7,12 @@ def mystery1(n)
   end
 end
 
+# Q1: mystery1(5) => 15
+# Q2: mystery1(10) => 155
+# Q3: mystery1(0) => inifinite loop / stack overflow error
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+
 def mystery2(n)
   if n < 10
     return n
@@ -15,6 +21,13 @@ def mystery2(n)
   end
 end
 
+# Q1: mystery2(123) => 6
+# Q2: mystery2(9005) => 14
+# Q3: mystery2(-123) => -123
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+# Condition: return n if n > -10  || n < 10
+
 def mystery3(n)
   if n == 0
     return 100
@@ -28,6 +41,13 @@ def mystery3(n)
   end
 end
 
+# Q1: mystery3(1) => 100
+# Q2: mystery3(13) => 100
+# Q3: mystery3(-6) => 200
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+
+
 def mystery4(b,e)
   if e == 0
     return 1
@@ -36,6 +56,12 @@ def mystery4(b,e)
   end
 end
 
+# Q1: mystery4(10, 2) => 100
+# Q2: mystery4(4, 3) => 64
+# Q3: mystery4(5, 0) => 1
+# Time Complexity: O(e)
+# Space Complexity: O(e)
+
 def mystery5(s)
   if s.length == 0
     return ""
@@ -44,6 +70,13 @@ def mystery5(s)
   end
 end
 
+# Q1: mystery5('hi') => '**'
+# Q1: mystery5('') => ''
+# Q1: mystery5('Hi, there!') => '**********'
+# Time Complexity: 0(s.length)
+# Space Complexity: O(s.length)
+# return '*' + mystery5(s[1..-1]) if s[0] is a letter
+
 def mystery6(s)
   if s == nil || s.length == 0
     return ""
@@ -56,6 +89,15 @@ def mystery6(s)
   end
 end
 
+
+# Q1: mystery6('goodnight moon') => ' moon goodnight'
+# Q2: mystery6('Ada Developer Academy') => ' Academy Developer Ada'
+# Q3: mystery6('Hi, there!') => ' there! Hi,'
+# Time Complexity: O(n) - n is the lenggth of s
+# Space Complexity: O(n) - n is the lenggth of s
+# Added fun:
+
+
 def mystery7(word)
   if word.length < 2
     return true
@@ -65,3 +107,9 @@ def mystery7(word)
     return mystery7(word[1..-2])
   end
 end
+
+# Q1: mystery7('cupcake') => false
+# Q2: mystery7('detected') => false
+# Q3: mystery7('eye') => true
+# Time Complexity: O(n) - n is the length of word
+# Space Complexity: O(n) - n is the length of word