Branches - Macaria

lib/linked_list.rb

@@ -12,120 +12,251 @@ 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
+  attr_reader :head
+
+  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
+  def add_first(value)
+    @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)
+    current = @head
 
-    # 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
+    until current.nil?
+      return true if current.data == value
+      current = current.next
     end
+    return false
+  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
+  # 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
+    current = @head
+    temp_max = @head.data
+    until current.nil?
+      if current.data > temp_max
+        temp_max = current.data
+      end
+      current = current.next
     end
+    return temp_max
+  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 min value in the linked list
+  # returns the data value and not the node
+  def find_min
+    if @head.nil?
+      return nil
+    end
+    current = @head
+    temp_min = @head.data
+    until current.nil?
+      if current.data < temp_min
+        temp_min = current.data
+      end
+      current = current.next
     end
+    return temp_min
+  end
 
-    # method to return the min value in the linked list
-    # returns the data value and not the node
-    def find_min
-      raise NotImplementedError
+  # method that returns the length of the singly linked list
+  def length
+    count = 0
+    current = @head
+    while current != nil
+      count += 1
+      current = current.next
     end
+    return count
+  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)
+    temp = @head
+    count = 0
+    while count < index && temp
+      temp = temp.next
+      count += 1
+    end
+    if (count == index)
+      return temp.data
+    else
+      return nil
+    end
+  end
 
-    # method that returns the length of the singly linked list
-    def length
-      raise NotImplementedError
+  # method to print all the values in the linked list
+  def visit
+    current = @head
+    until current.nil?
+      puts current.data
+      current = current.next
     end
+  end
+
+  # method to delete the first node found with specified value
+  def delete(value)
+    return nil if @head.nil?
+
+    current = @head
+    prev = nil
 
-    # 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
+    until current.data == value
+      prev = current
+      current = current.next
     end
 
-    # method to print all the values in the linked list
-    def visit
-      raise NotImplementedError
+    if prev.nil?
+      @head = current.next
+    else
+      prev.next = current.next
     end
+  end
 
-    # method to delete the first node found with specified value
-    def delete(value)
-      raise NotImplementedError
+  # method to reverse the singly linked list
+  # note: the nodes should be moved and not just the values in the nodes
+  def reverse
+    if @head.nil?
+      return @head
     end
 
-    # 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
+
+    until current.next.nil?
+      temp = current.next
+      current.next = previous
+      previous = current
+      current = temp
     end
 
+    current.next = previous
+    @head = current
+  end
+
+  ## Advanced Exercises
+  # returns the value at the middle element in the singly linked list
+  def find_middle_value
+    raise NotImplementedError
+  end
 
-    ## Advanced Exercises
-    # returns the value at the middle element in the singly linked list
-    def find_middle_value
-      raise NotImplementedError
+  # 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)
+    current = @head
+    n_counter = @head
+
+    counter = 0
+
+    n.times do
+      if !n_counter.nil? && !n_counter.next.nil?
+        n_counter = n_counter.next
+      else
+        return nil
+      end
     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
+    until n_counter.next.nil?
+      n_counter = n_counter.next
+      current = current.next
     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.
-    def has_cycle
-      raise NotImplementedError
+    return current.data
+  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.
+  def has_cyclez
+    current = @head
+    fast_pt = current
+    slow_pt = current
+
+    until fast_pt.next.nil?
+      if fast_pt == slow_pt
+        return true
+      end
+      fast_pt = fast_pt.next
+      fast_pt = fast_pt.next
+      slow_pt = slow_pt.next
     end
+    return false
+  end
 
+  # Additional Exercises
+  # returns the value in the first node
+  # returns nil if the list is empty
+  def get_first
+    if @head.nil?
+      return nil
+    else
+      return @head.data
+    end
+  end
 
-    # Additional Exercises 
-    # returns the value in the first node
-    # returns nil if the list is empty
-    def get_first
-      raise NotImplementedError
+  # method that inserts a given value as a new last node in the linked list
+  def add_last(value)
+    temp = @head
+    while temp != nil && temp.next != nil
+      temp = temp.next
     end
+    last_node = Node.new(value)
 
-    # method that inserts a given value as a new last node in the linked list
-    def add_last(value)
-      raise NotImplementedError
+    if (temp != nil)
+      temp.next = last_node
+    else
+      @head = last_node
     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
+    return @head
+  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
+    if @head.nil?
+      return nil
     end
 
-    # 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
+    until 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
+    return current.data
+  end
+
+  # 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
+  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