From 6563b39c1d2aff6bb5fa3a4d6d15ee23f5eb27a9 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 15:36:14 -0400
Subject: [PATCH 01/10] completed basic, did some advnaced

---
 lib/linked_list.rb | 326 +++++++++++++++++++++++++++++----------------
 1 file changed, 212 insertions(+), 114 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 0de1ee00..54bcc347 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -12,150 +12,248 @@ def initialize(value, next_node = nil)
 
 # Defines the singly linked list
 class LinkedList
-    def initialize
-      @head = nil # keep the head private. Not accessible outside this class
-    end
+  def initialize
+    @head = nil # keep the head private. Not accessible outside this class
+  end
 
-    # method to add a new node with the specific data value in the linked list
-    # insert the new node at the beginning of the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def add_first(value)
-      raise NotImplementedError
+  # method to add a new node with the specific data value in the linked list
+  # insert the new node at the beginning of the linked list
+  # Time Complexity: O(1)
+  # Space Complexity: O(1)
+  def add_first(value)
+    if @head
+      second = @head
+      @head = Node.new(value, second)
+    else
+      @head = Node.new(value)
     end
+  end
 
-    # method to find if the linked list contains a node with specified value
-    # returns true if found, false otherwise
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def search(value)
-      raise NotImplementedError
+  # method to find if the linked list contains a node with specified value
+  # returns true if found, false otherwise
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def search(value)
+    if @head == nil
+      return false
+    end
+    return search_help(value) != nil
+  end
+  def search_help(value)
+    current = @head
+    while current != nil
+      if current.data == value
+        return current
+      else
+        current = current.next
+      end
     end
+    return nil
+  end
 
-    # method to return the max value in the linked list
-    # returns the data value and not the node
-    def find_max
-      raise NotImplementedError
+  # method to return the max value in the linked list
+  # returns the data value and not the node
+  def find_max
+    if @head == nil
+      return nil
     end
+    max = @head.data
+    current = @head
+    while current != nil
+      if current.data > max
+        max = current.data
+      end
+      current = current.next
+    end
+    return max
+  end
 
-    # method to return the min value in the linked list
-    # returns the data value and not the node
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def find_min
-      raise NotImplementedError
+  # method to return the min value in the linked list
+  # returns the data value and not the node
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def find_min
+    if @head == nil
+      return nil
     end
+    min = @head.data
+    current = @head
+    while current != nil
+      if current.data < min
+        min = current.data
+      end
+      current = current.next
+    end
+    return min
+  end
 
 
-    # method that returns the length of the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def length
-      raise NotImplementedError
+  # method that returns the length of the singly linked list
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def length
+    if @head == nil
+      return 0
     end
-
-    # method that returns the value at a given index in the linked list
-    # index count starts at 0
-    # returns nil if there are fewer nodes in the linked list than the index value
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def get_at_index(index)
-      raise NotImplementedError
+    current = @head
+    length = 1
+    while current != nil
+      length += 1
+      current = current.next
     end
+    return length
+  end
 
-    # method to print all the values in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def visit
-      raise NotImplementedError
+  # method that returns the value at a given index in the linked list
+  # index count starts at 0
+  # returns nil if there are fewer nodes in the linked list than the index value
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def get_at_index(index)
+    return get_node_at_index.data
+  end
+  def get_node_at_index(index)
+    length = this.length
+    if length < index
+      return nil
     end
-
-    # method to delete the first node found with specified value
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def delete(value)
-      raise NotImplementedError
+    current = @head
+    (0..length-1).each do |i|
+      if i == index
+        return current
+      end
+      current = current.next
     end
+  end
 
-    # method to reverse the singly linked list
-    # note: the nodes should be moved and not just the values in the nodes
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def reverse
-      raise NotImplementedError
+  # method to print all the values in the linked list
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def visit
+    current = @head
+    while current != nil
+      puts current.data
+      current = current.next
     end
+  end
 
+  # method to delete the first node found with specified value
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def delete(value)
+    target = search_help(value)
+    after_target = target.next
+    target.next = nil
+    before_target_index = this.length - 2
+    before_target = get_node_at_index(before_target_index)
+    before_target.next = after_target
+  end
 
-    ## Advanced Exercises
-    # returns the value at the middle element in the singly linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def find_middle_value
-      raise NotImplementedError
+  # method to reverse the singly linked list
+  # note: the nodes should be moved and not just the values in the nodes
+  # Time Complexity: O(n)
+  # Space Complexity: O(n)
+  def reverse
+    new_list = LinkedList.new
+    current = @head
+    while current != nil
+      new_list.add_first(current)
+      current = current.next
     end
+    this = new_list
+  end
 
-    # find the nth node from the end and return its value
-    # assume indexing starts at 0 while counting to n
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def find_nth_from_end(n)
-      raise NotImplementedError
-    end
 
-    # checks if the linked list has a cycle. A cycle exists if any node in the
-    # linked list links to a node already visited.
-    # returns true if a cycle is found, false otherwise.
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def has_cycle
-      raise NotImplementedError
-    end
+  ## Advanced Exercises
+  # returns the value at the middle element in the singly linked list
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def find_middle_value
+    length = this.length
+    middle_index = length/2
+    return get_at_index(middle_index)
+  end
 
+  # find the nth node from the end and return its value
+  # assume indexing starts at 0 while counting to n
+  # Time Complexity: O(n)
+  # Space Complexity: O(1)
+  def find_nth_from_end(n)
+    length = this.length
+    nth_from_end_index = length - 1 - n
+    return get_at_index(nth_from_end_index)
+  end
 
-    # Additional Exercises 
-    # returns the value in the first node
-    # returns nil if the list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def get_first
-      raise NotImplementedError
+  # checks if the linked list has a cycle. A cycle exists if any node in the
+  # linked list links to a node already visited.
+  # returns true if a cycle is found, false otherwise.
+  # Time Complexity: ?
+  # Space Complexity: ?
+  def has_cycle
+    current = @head
+    seen_nodes = []
+    # while current != nil || has_node?(current)
+    #   current = current.next
+    #   if current == nil
+    #     return false
+    #   end
+    #   if has_node
+    # end
+  end
+  def has_node?(array, node)
+    array.each do |current_node|
+      if current_node == node
+        return true
+      end
     end
+    return false
+  end
 
-    # method that inserts a given value as a new last node in the linked list
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def add_last(value)
-      raise NotImplementedError
-    end
 
-    # method that returns the value of the last node in the linked list
-    # returns nil if the linked list is empty
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def get_last
-      raise NotImplementedError
-    end
+  # Additional Exercises 
+  # returns the value in the first node
+  # returns nil if the list is empty
+  # Time Complexity: ?
+  # Space Complexity: ?
+  def get_first
+    raise NotImplementedError
+  end
 
-    # method to insert a new node with specific data value, assuming the linked
-    # list is sorted in ascending order
-    # Time Complexity: ?
-    # Space Complexity: ?
-    def insert_ascending(value)
-      raise NotImplementedError
-    end
+  # method that inserts a given value as a new last node in the linked list
+  # Time Complexity: ?
+  # Space Complexity: ?
+  def add_last(value)
+    raise NotImplementedError
+  end
+
+  # method that returns the value of the last node in the linked list
+  # returns nil if the linked list is empty
+  # Time Complexity: ?
+  # Space Complexity: ?
+  def get_last
+    raise NotImplementedError
+  end
 
-    # Helper method for tests
-    # Creates a cycle in the linked list for testing purposes
-    # Assumes the linked list has at least one node
-    def create_cycle
-      return if @head == nil # don't do anything if the linked list is empty
+  # method to insert a new node with specific data value, assuming the linked
+  # list is sorted in ascending order
+  # Time Complexity: ?
+  # Space Complexity: ?
+  def insert_ascending(value)
+    raise NotImplementedError
+  end
 
-      # navigate to last node
-      current = @head
-      while current.next != nil
-          current = current.next
-      end
+  # Helper method for tests
+  # Creates a cycle in the linked list for testing purposes
+  # Assumes the linked list has at least one node
+  def create_cycle
+    return if @head == nil # don't do anything if the linked list is empty
 
-      current.next = @head # make the last node link to first node
+    # navigate to last node
+    current = @head
+    while current.next != nil
+        current = current.next
     end
+
+    current.next = @head # make the last node link to first node
+  end
 end

From cfd57d4bf1c565d6e86669b253e8419692d23363 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 15:42:25 -0400
Subject: [PATCH 02/10] fixed bug in length

---
 lib/linked_list.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 54bcc347..471bc5c4 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -96,7 +96,7 @@ def length
       return 0
     end
     current = @head
-    length = 1
+    length = 0
     while current != nil
       length += 1
       current = current.next

From 6d49e35ce2346a5e6fd7c89c819457c71662b1f4 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 15:43:38 -0400
Subject: [PATCH 03/10] fixed bug in get_index

---
 lib/linked_list.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 471bc5c4..2fcfa8f8 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -110,7 +110,7 @@ def length
   # Time Complexity: O(n)
   # Space Complexity: O(1)
   def get_at_index(index)
-    return get_node_at_index.data
+    return get_node_at_index(index).data
   end
   def get_node_at_index(index)
     length = this.length

From 3410ad5854a2c82408b886b316891affbe749052 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 15:46:23 -0400
Subject: [PATCH 04/10] replaced this with right ruby keyword, self

---
 lib/linked_list.rb | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 2fcfa8f8..b813f09e 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -13,7 +13,7 @@ def initialize(value, next_node = nil)
 # Defines the singly linked list
 class LinkedList
   def initialize
-    @head = nil # keep the head private. Not accessible outside this class
+    @head = nil # keep the head private. Not accessible outside self class
   end
 
   # method to add a new node with the specific data value in the linked list
@@ -113,7 +113,7 @@ def get_at_index(index)
     return get_node_at_index(index).data
   end
   def get_node_at_index(index)
-    length = this.length
+    length = self.length
     if length < index
       return nil
     end
@@ -144,7 +144,7 @@ def delete(value)
     target = search_help(value)
     after_target = target.next
     target.next = nil
-    before_target_index = this.length - 2
+    before_target_index = self.length - 2
     before_target = get_node_at_index(before_target_index)
     before_target.next = after_target
   end
@@ -160,7 +160,7 @@ def reverse
       new_list.add_first(current)
       current = current.next
     end
-    this = new_list
+    self = new_list
   end
 
 
@@ -169,7 +169,7 @@ def reverse
   # Time Complexity: O(n)
   # Space Complexity: O(1)
   def find_middle_value
-    length = this.length
+    length = self.length
     middle_index = length/2
     return get_at_index(middle_index)
   end
@@ -179,7 +179,7 @@ def find_middle_value
   # Time Complexity: O(n)
   # Space Complexity: O(1)
   def find_nth_from_end(n)
-    length = this.length
+    length = self.length
     nth_from_end_index = length - 1 - n
     return get_at_index(nth_from_end_index)
   end

From 1b111246ec68bf755a12fea03e9f9574ac451c43 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 15:50:11 -0400
Subject: [PATCH 05/10] can't re-assign self, so changed reverse
 implementation, first attempt

---
 lib/linked_list.rb | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index b813f09e..4f125b31 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -160,7 +160,9 @@ def reverse
       new_list.add_first(current)
       current = current.next
     end
-    self = new_list
+    @head.next = nil
+    @head.data = nil
+    @head = new_list
   end
 
 

From e9ab1a665009a82f52f5ef10c743488919ac9bb3 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 19:01:56 -0400
Subject: [PATCH 06/10] added get_first

---
 lib/linked_list.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 4f125b31..b58a3317 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -218,7 +218,11 @@ def has_node?(array, node)
   # Time Complexity: ?
   # Space Complexity: ?
   def get_first
-    raise NotImplementedError
+    if @head
+      return @head
+    else
+      return nil
+    end
   end
 
   # method that inserts a given value as a new last node in the linked list

From 0fdb1b71cb47c4ea87f89054b40aac26460934c6 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 19:07:15 -0400
Subject: [PATCH 07/10] fixed get_at_index for nil case

---
 lib/linked_list.rb | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index b58a3317..2e741ad3 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -110,7 +110,12 @@ def length
   # Time Complexity: O(n)
   # Space Complexity: O(1)
   def get_at_index(index)
-    return get_node_at_index(index).data
+    node = get_node_at_index(index)
+    if node
+      return node.data
+    else
+      return nil
+    end
   end
   def get_node_at_index(index)
     length = self.length

From 27fb9a65d90a862249e1c1468bef1d0fada59f1b Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 19:09:39 -0400
Subject: [PATCH 08/10] added additional nil return case for get_node_at_index

---
 lib/linked_list.rb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 2e741ad3..6e0466da 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -123,12 +123,13 @@ def get_node_at_index(index)
       return nil
     end
     current = @head
-    (0..length-1).each do |i|
+    (0..(length-1)).each do |i|
       if i == index
         return current
       end
       current = current.next
     end
+    return nil
   end
 
   # method to print all the values in the linked list

From f8ab2f64c10d5f759780f3b592d767102bfd829d Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 19:13:04 -0400
Subject: [PATCH 09/10] changed list reassignment statement in #reverse to
 actually work, instead of tring to assign a list to a node

---
 lib/linked_list.rb | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 6e0466da..c1481778 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -167,8 +167,7 @@ def reverse
       current = current.next
     end
     @head.next = nil
-    @head.data = nil
-    @head = new_list
+    @head = new_list.get_first
   end
 
 

From 0d5884d1bdd3f21b3685f09b76346194ff105bd3 Mon Sep 17 00:00:00 2001
From: saintmedusa <yasmineoshaugh@gmail.com>
Date: Thu, 27 Aug 2020 19:17:39 -0400
Subject: [PATCH 10/10] moved my helper methods to private

---
 lib/linked_list.rb | 55 +++++++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 25 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index c1481778..4233234c 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -39,17 +39,6 @@ def search(value)
     end
     return search_help(value) != nil
   end
-  def search_help(value)
-    current = @head
-    while current != nil
-      if current.data == value
-        return current
-      else
-        current = current.next
-      end
-    end
-    return nil
-  end
 
   # method to return the max value in the linked list
   # returns the data value and not the node
@@ -117,20 +106,6 @@ def get_at_index(index)
       return nil
     end
   end
-  def get_node_at_index(index)
-    length = self.length
-    if length < index
-      return nil
-    end
-    current = @head
-    (0..(length-1)).each do |i|
-      if i == index
-        return current
-      end
-      current = current.next
-    end
-    return nil
-  end
 
   # method to print all the values in the linked list
   # Time Complexity: O(n)
@@ -267,4 +242,34 @@ def create_cycle
 
     current.next = @head # make the last node link to first node
   end
+
+  private
+
+  def get_node_at_index(index)
+    length = self.length
+    if length < index
+      return nil
+    end
+    current = @head
+    (0..(length-1)).each do |i|
+      if i == index
+        return current
+      end
+      current = current.next
+    end
+    return nil
+  end
+
+  def search_help(value)
+    current = @head
+    while current != nil
+      if current.data == value
+        return current
+      else
+        current = current.next
+      end
+    end
+    return nil
+  end
+
 end