From 25cab4f3fb13ff55561fbcdde57884226d3fd718 Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Sun, 16 Feb 2020 18:49:20 -0800
Subject: [PATCH 1/8] Implemented add_first and search method

---
 lib/linked_list.rb       | 12 ++++++++++--
 test/linked_list_test.rb |  1 -
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 8dee5e8d..168f58a4 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -19,13 +19,20 @@ def initialize
     # 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
     def add_first(value)
-      raise NotImplementedError
+      @head = Node.new(value, @head)
     end
 
     # method to find if the linked list contains a node with specified value
     # returns true if found, false otherwise
     def search(value)
-      raise NotImplementedError
+      current = @head
+
+      until current.nil?
+        return true if current.data == value
+
+        current = current.next
+      end
+      return false
     end
 
     # method to return the max value in the linked list
@@ -129,3 +136,4 @@ def create_cycle
       current.next = @head # make the last node link to first node
     end
 end
+
diff --git a/test/linked_list_test.rb b/test/linked_list_test.rb
index 22b55ef0..4b84cd0d 100644
--- a/test/linked_list_test.rb
+++ b/test/linked_list_test.rb
@@ -1,6 +1,5 @@
 require 'minitest/autorun'
 require 'minitest/reporters'
-require 'minitest/skip_dsl'
 
 require_relative 'test_helper'
 

From 4b093bcc0b3a7d865cf9d9ff9cfea7dd560ed76f Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Sun, 16 Feb 2020 19:07:52 -0800
Subject: [PATCH 2/8] Implemented find_min and find_max methods

---
 lib/linked_list.rb | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 168f58a4..2dae7fea 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -29,7 +29,6 @@ def search(value)
 
       until current.nil?
         return true if current.data == value
-
         current = current.next
       end
       return false
@@ -38,19 +37,35 @@ def search(value)
     # method to return the max value in the linked list
     # returns the data value and not the node
     def find_max
-      raise NotImplementedError
+      current = @head
+      max = current
+      return nil if current.nil?
+
+      until current.nil?
+        max = current if current.data > max.data
+        current = current.next
+      end
+      return max.data
     end
 
     # method to return the min value in the linked list
     # returns the data value and not the node
     def find_min
-      raise NotImplementedError
+      current = @head
+      min = current
+      return nil if current.nil?
+
+      until current.nil?
+        min = current if current.data < min.data
+        current = current.next
+      end
+      return min.data
     end
 
 
     # method that returns the length of the singly linked list
     def length
-      raise NotImplementedError
+
     end
 
     # method that returns the value at a given index in the linked list

From de033ca9f42c68c9e7cca37b20b52988566b949b Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Sun, 16 Feb 2020 19:25:14 -0800
Subject: [PATCH 3/8] Implemented length and get_at_index methods

---
 lib/linked_list.rb | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 2dae7fea..046f3b81 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -65,14 +65,30 @@ def find_min
 
     # method that returns the length of the singly linked list
     def length
-
+      current = @head
+      length = 0
+      return 0 if current.nil?
+        
+      until current.nil?
+        current = current.next
+        length += 1
+      end
+      return length
     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
     def get_at_index(index)
-      raise NotImplementedError
+      current = @head
+      current_index = 0
+        
+      index.times do |i|
+        return nil if current.nil?
+        current = current.next
+      end
+      
+      return current.data
     end
 
     # method to print all the values in the linked list

From 9d860c74473378adbcf71a7d278f11c49d0a4bac Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Sun, 16 Feb 2020 20:14:44 -0800
Subject: [PATCH 4/8] Implemented get_first, get_last and add_last methods

---
 lib/linked_list.rb | 44 +++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 39 insertions(+), 5 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 046f3b81..e93c5ae3 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -93,12 +93,26 @@ def get_at_index(index)
 
     # method to print all the values in the linked list
     def visit
-      raise NotImplementedError
+      current = @head
+
+      until current.nil?
+        print current.data
+        current = current.next
+      end
     end
 
     # method to delete the first node found with specified value
     def delete(value)
-      raise NotImplementedError
+      current = @head
+
+      return nil if current.nil?
+      until current.nil?
+        to_delete = current if current.data == value
+        current = current.next
+      end
+
+      to_delete.previous.next = to_delete.next
+      to_delete.next.previous = to_delete.previous
     end
 
     # method to reverse the singly linked list
@@ -132,18 +146,38 @@ def has_cycle
     # returns the value in the first node
     # returns nil if the list is empty
     def get_first
-      raise NotImplementedError
+      current = @head
+
+      return nil if current.nil?
+      return @head.data
     end
 
     # method that inserts a given value as a new last node in the linked list
     def add_last(value)
-      raise NotImplementedError
+      current = @head
+
+      if current.nil?
+        @head = Node.new(value)
+        return
+      end
+
+      until current.next.nil?
+        current = current.next
+      end
+
+      current.next = Node.new(value)
     end
 
     # method that returns the value of the last node in the linked list
     # returns nil if the linked list is empty
     def get_last
-      raise NotImplementedError
+      current = @head
+
+      return nil if current.nil?
+      until current.next.nil?
+        current = current.next
+      end
+      return current.data
     end
 
     # method to insert a new node with specific data value, assuming the linked

From 6a064efb76ac920a33e8126ce5f30a1e6087a391 Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Sun, 16 Feb 2020 20:38:30 -0800
Subject: [PATCH 5/8] Implemented delete method

---
 lib/linked_list.rb | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index e93c5ae3..388901d0 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -104,15 +104,19 @@ def visit
     # method to delete the first node found with specified value
     def delete(value)
       current = @head
+      previous = nil
 
       return nil if current.nil?
-      until current.nil?
-        to_delete = current if current.data == value
+      until current.data == value
+        previous = current
         current = current.next
       end
 
-      to_delete.previous.next = to_delete.next
-      to_delete.next.previous = to_delete.previous
+      if previous.nil?
+        @head = current.next
+      else
+        previous.next = current.next
+      end
     end
 
     # method to reverse the singly linked list
@@ -183,7 +187,21 @@ def get_last
     # method to insert a new node with specific data value, assuming the linked
     # list is sorted in ascending order
     def insert_ascending(value)
-      raise NotImplementedError
+      current = @head
+
+      if current.nil?
+        @head = Node.new(value)
+      end
+
+      until current.nil?        
+        if value.data > last.data && value.data < current.data
+          new_node = Node.new(value, current.next)
+          current.next = new_node
+          return
+        else
+          current = current.next
+        end
+      end
     end
 
     # Helper method for tests

From 2a0c65230ea1548cc97063c744595272cdb5f310 Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Wed, 19 Feb 2020 13:06:22 -0800
Subject: [PATCH 6/8] Impletemented reverse method

---
 lib/linked_list.rb | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 388901d0..134e174b 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -122,7 +122,17 @@ def delete(value)
     # method to reverse the singly linked list
     # note: the nodes should be moved and not just the values in the nodes
     def reverse
-      raise NotImplementedError
+      current = @head
+      previous = nil
+
+      return nil if current.nil?
+      until current.nil?
+        temp = current
+        current.next = previous
+        current = current.next
+        previous = temp
+      end
+      @head = previous
     end
 
 

From e7e6fc3edfad159e55f67e4e7146fd1878fabfa7 Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Wed, 19 Feb 2020 17:58:10 -0800
Subject: [PATCH 7/8] Fixed reverse method

---
 lib/linked_list.rb | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 134e174b..3efc9fbe 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -125,11 +125,10 @@ def reverse
       current = @head
       previous = nil
 
-      return nil if current.nil?
       until current.nil?
         temp = current
-        current.next = previous
         current = current.next
+        temp.next = previous
         previous = temp
       end
       @head = previous
@@ -139,13 +138,36 @@ def reverse
     ## Advanced Exercises
     # returns the value at the middle element in the singly linked list
     def find_middle_value
-      raise NotImplementedError
+      current = @head
+      middle = current
+
+      return nil if current.nil?
+      until current.nil?
+        middle.next = middle
+        current.next.next = current
+      end
+      return middle
     end
 
     # find the nth node from the end and return its value
     # assume indexing starts at 0 while counting to n
     def find_nth_from_end(n)
-      raise NotImplementedError
+      current = @head
+      from_end = current
+
+      return nil if current.nil?
+
+      n.times do
+        return nil if current.next.nil?
+        current = current.next
+      end
+      
+      until current.next.nil?
+        return from_end.data if from_end.next.nil?
+        from_end = from_end.next
+        current = current.next
+      end
+      return from_end.data
     end
 
     # checks if the linked list has a cycle. A cycle exists if any node in the

From b04e642f969ffb0422fac143575cd98e0790e60b Mon Sep 17 00:00:00 2001
From: Julia Bouvier <juliabouv@gmail.com>
Date: Wed, 19 Feb 2020 18:01:12 -0800
Subject: [PATCH 8/8] Implemented has_cycle

---
 lib/linked_list.rb | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 3efc9fbe..cfcff9af 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -174,7 +174,15 @@ def find_nth_from_end(n)
     # linked list links to a node already visited.
     # returns true if a cycle is found, false otherwise.
     def has_cycle
-      raise NotImplementedError
+      slow = @head
+      fast = @head
+
+      until fast.nil?
+        slow = slow.next
+        fast = fast.next.next
+        return true if slow == fast
+      end
+      return false
     end