Branches - Julia Bouvier

lib/linked_list.rb

@@ -19,99 +19,229 @@ 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
     # 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
+      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
     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
+      previous = nil
+
+      return nil if current.nil?
+      until current.data == value
+        previous = current
+        current = current.next
+      end
+
+      if previous.nil?
+        @head = current.next
+      else
+        previous.next = 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
     def reverse
-      raise NotImplementedError
+      current = @head
+      previous = nil
+
+      until current.nil?
+        temp = current
+        current = current.next
+        temp.next = previous
+        previous = temp
+      end
+      @head = previous
     end
 
 
     ## 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
     # 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
 
 
     # Additional Exercises 
     # 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
     # 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
@@ -129,3 +259,4 @@ def create_cycle
       current.next = @head # make the last node link to first node
     end
 end
+

test/linked_list_test.rb

@@ -1,6 +1,5 @@
 require 'minitest/autorun'
 require 'minitest/reporters'
-require 'minitest/skip_dsl'
 
 require_relative 'test_helper'