From a3c6ce0c408902a6d0dea279eb9fe2f25d30c2c1 Mon Sep 17 00:00:00 2001
From: Bitaman <b.amani.s@gmail.com>
Date: Sun, 25 Aug 2019 22:01:44 -0700
Subject: [PATCH 1/2] all test are passing

---
 lib/linked_list.rb | 371 +++++++++++++++++++++++++++++++--------------
 1 file changed, 258 insertions(+), 113 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 501c60fb..86b6bd2a 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -12,152 +12,297 @@ 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:
+  # Space Complexity
+  def add_first(value)
+    # raise NotImplementedError
+    if @head
+      temp_node = @head
+      new_node = Node.new(value, temp_node)
+      @head = new_node
+    else
+      @head = Node.new(value)
     end
+    return @head.data
+  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:
+  # Space Complexity
+  def search(value)
+    # raise NotImplementedError
+    if !@head
+      return false
+    else
+      current_node = @head
+      while current_node != nil
+        if current_node.data == value
+          return true
+        else
+          current_node = current_node.next
+        end
+      end
+      return false
     end
+  end
 
-    # method to return the max value in the linked list
-    # returns the data value and not the node
-    # Time Complexity:  
-    # Space Complexity
-    def find_max
-      raise NotImplementedError
+  # method to return the max value in the linked list
+  # returns the data value and not the node
+  # Time Complexity:
+  # Space Complexity
+  def find_max
+    #  raise NotImplementedError
+    if !@head
+      return nil
+    else
+      current_node = @head
+      max = current_node.data
+      while current_node != nil
+        if current_node.data > max
+          max = current_node.data
+        end
+        current_node = current_node.next
+      end
+      return max
     end
+  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:
+  # Space Complexity
+  def find_min
+    # raise NotImplementedError
+    if !@head
+      return nil
+    else
+      current_node = @head
+      min = current_node.data
+      while current_node != nil
+        if current_node.data < min
+          min = current_node.data
+        end
+        current_node = current_node.next
+      end
+      return min
     end
+  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:
+  # Space Complexity
+  def length
+    # raise NotImplementedError
+    if !@head
+      return 0
+    else
+      i = 0
+      current_node = @head
+      while current_node != nil
+        i += 1
+        current_node = current_node.next
+      end
+      return i
     end
+  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
+  # 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
+    return if !@head
+    i = 0
+    current_node = @head
+    until i == index
+      current_node = current_node.next
+      i += 1
     end
+    return current_node.data
+  end
 
-    # method to print all the values in the linked list
-    # Time Complexity:  
-    # Space Complexity
-    def visit
-      raise NotImplementedError
+  # method to print all the values in the linked list
+  # Time Complexity:
+  # Space Complexity
+  def visit
+    # raise NotImplementedError
+    current_node = @head
+    while current_node != nill
+      puts "Node value #{current_node.data}"
+      current_node = current_node.next
     end
+  end
 
-    # method to delete the first node found with specified value
-    # Time Complexity:  
-    # Space Complexity
-    def delete(value)
-      raise NotImplementedError
+  # method to delete the first node found with specified value
+  # Time Complexity:
+  # Space Complexity
+  def delete(value)
+    #raise NotImplementedError
+    current = @head
+    before = nil
+    while current
+      if current.data == value
+        if !before && !current.next
+          @head = nil
+        elsif !before
+          @head = current.next
+        else
+          before.next = current.next
+        end
+        return "deleted"
+      end
+      before = current
+      current = current.next
     end
+    return nil
+  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
-    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
+    return if @head == nil or @head.next == nil
 
+    first = @head
+    second = first.next
+    third = second.next
+    first.next = nil
 
-    ## Advanced Exercises
-    # returns the value at the middle element in the singly linked list
-    # Time Complexity:  
-    # Space Complexity
-    def find_middle_value
-      raise NotImplementedError
+    until third.nil?
+      second.next = first
+      first = second
+      second = third
+      third = third.next
     end
+    second.next = first
+    @head = second
+  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
+  ## Advanced Exercises
+  # returns the value at the middle element in the singly linked list
+  # Time Complexity:
+  # Space Complexity
+  def find_middle_value
+    # raise NotImplementedError
+    if !@head
+      return nil
+    else
+      l = self.length
+      j = l / 2
+      current = @head
+      (j - 1).times do
+        current = current.next
+      end
+      retrun current.data
     end
+  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
+  # 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
+    if !@head || (n >= self.length)
+      return nil
+    else
+      l = self.length
+      i = l - (n + 1)
+      current = @head
+      i.times do
+        current = current.next
+      end
+      return current.data
     end
+  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
 
-    # 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 that inserts a given value as a new last node in the linked list
-    # Time Complexity:  
-    # Space Complexity
-    def add_last(value)
-      raise NotImplementedError
+  # 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
+    if @head
+      return @head.data
+    else
+      return nil
     end
+  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
+  # 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
+    if @head
+      current_node = @head
+      while current_node.next != nil
+        current_node = current_node.next
+      end
+      current_node.next = Node.new(value)
+    else
+      @head = Node.new(value)
     end
+  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
+  # 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
+    if !@head
+      return nil
+    else
+      current_node = @head
+      while current_node.next != nil
+        current_node = current_node.next
+      end
     end
+    return current_node.data
+  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 5aa24d75919ae38e44a5d1cfdb6f51d1c94796bd Mon Sep 17 00:00:00 2001
From: Bitaman <b.amani.s@gmail.com>
Date: Sun, 25 Aug 2019 23:35:44 -0700
Subject: [PATCH 2/2] added time and space complexity

---
 lib/linked_list.rb | 56 +++++++++++++++++++++++-----------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/lib/linked_list.rb b/lib/linked_list.rb
index 86b6bd2a..120768e3 100644
--- a/lib/linked_list.rb
+++ b/lib/linked_list.rb
@@ -18,8 +18,8 @@ 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
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(1)
+  # Space Complexity:O(1)
   def add_first(value)
     # raise NotImplementedError
     if @head
@@ -34,8 +34,8 @@ def add_first(value)
 
   # method to find if the linked list contains a node with specified value
   # returns true if found, false otherwise
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def search(value)
     # raise NotImplementedError
     if !@head
@@ -55,8 +55,8 @@ def search(value)
 
   # method to return the max value in the linked list
   # returns the data value and not the node
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def find_max
     #  raise NotImplementedError
     if !@head
@@ -76,8 +76,8 @@ def find_max
 
   # method to return the min value in the linked list
   # returns the data value and not the node
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def find_min
     # raise NotImplementedError
     if !@head
@@ -96,8 +96,8 @@ def find_min
   end
 
   # method that returns the length of the singly linked list
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def length
     # raise NotImplementedError
     if !@head
@@ -116,8 +116,8 @@ def length
   # 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
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def get_at_index(index)
     #  raise NotImplementedError
     return if !@head
@@ -131,8 +131,8 @@ def get_at_index(index)
   end
 
   # method to print all the values in the linked list
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def visit
     # raise NotImplementedError
     current_node = @head
@@ -143,8 +143,8 @@ def visit
   end
 
   # method to delete the first node found with specified value
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def delete(value)
     #raise NotImplementedError
     current = @head
@@ -168,8 +168,8 @@ def delete(value)
 
   # 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
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def reverse
     # raise NotImplementedError
     return if @head == nil or @head.next == nil
@@ -191,8 +191,8 @@ def reverse
 
   ## Advanced Exercises
   # returns the value at the middle element in the singly linked list
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def find_middle_value
     # raise NotImplementedError
     if !@head
@@ -210,8 +210,8 @@ def find_middle_value
 
   # find the nth node from the end and return its value
   # assume indexing starts at 0 while counting to n
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def find_nth_from_end(n)
     # raise NotImplementedError
     if !@head || (n >= self.length)
@@ -239,8 +239,8 @@ def has_cycle
   # Additional Exercises
   # returns the value in the first node
   # returns nil if the list is empty
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(1)
+  # Space Complexity:O(1)
   def get_first
     # raise NotImplementedError
     if @head
@@ -251,8 +251,8 @@ def get_first
   end
 
   # method that inserts a given value as a new last node in the linked list
-  # Time Complexity:
-  # Space Complexity
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def add_last(value)
     # raise NotImplementedError
     if @head
@@ -268,8 +268,8 @@ def add_last(value)
 
   # 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
+  # Time Complexity:O(n)
+  # Space Complexity:O(1)
   def get_last
     # raise NotImplementedError
     if !@head