Sara - Branches

lib/linked_list.rb

@@ -19,99 +19,270 @@ 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
+      # 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
+      # raise 
+      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
-    end
+      # raise NotImplementedError
+      current = @head
+      return nil if current.nil?
 
+
+      max = @head
+
+      until current.nil?
+        if current.data > max.data
+          max = current
+        end
+        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
-    end
+      # raise NotImplementedError
+      return nil if @head.nil?
 
+      current = @head
+      min = @head.data
+
+      until 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
     def length
-      raise NotImplementedError
+      # raise NotImplementedError
+      size = 0
+      current = @head
+
+      until current.nil?
+        current = current.next
+        size = size + 1
+      end
+
+
+      return size
     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
+      # raise NotImplementedError
+      current = @head
+
+      index.times do 
+        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
+      # 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
+      # raise NotImplementedError
+      current = @head
+      return nil if current.nil?
+
+
+      previous = nil
+
+      until current.data == value
+        return nil if current.nil?
+        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
+      # raise NotImplementedError
+      return if @head.nil?
+
+      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
+      # raise NotImplementedError
+      length = self.length
+      if length % 2 == 0
+        value = (length / 2) - 1
+      else
+        value = (length / 2)
+      end
+
     end
 
+    # fast = @root
+    # slow = @root
+    # until fast.nil? 
+
     # 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
+      # raise NotImplementedError
+      current = @head
+      return nil if current.nil?
+
+
+      nth_head = @head
+
+      n.times do
+        return nil if nth_head.next.nil?
+        nth_head = nth_head.next
+      end
+
+      until nth_head.next.nil?
+        return current.data if current.next.nil?
+        current = current.next
+        nth_head = nth_head.next
+      end
+      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_cycle
-      raise NotImplementedError
+      # raise NotImplementedError
+      return if @head == nil
+
+      current.next = @head
     end
 
+
+
 
     # Additional Exercises 
     # returns the value in the first node
     # returns nil if the list is empty
     def get_first
-      raise NotImplementedError
+      # raise NotImplementedError
+      if @head.nil?
+        return nil
+      else 
+        return @head.data
+      end
     end
 
     # method that inserts a given value as a new last node in the linked list
     def add_last(value)
-      raise NotImplementedError
+      # raise NotImplementedError
+      current = @head
+
+      if current.nil?
+        @head = Node.new(value)
+        return @head
+      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
+      # 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
+      # raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head
+      if value < current.data
+        self.first(value)
+      end
+
+      until current.next.nil?
+        current_value = current.data
+        next_value = current.next.data
+
+        if value > current_value && value < next_value
+          new_node = Node.new(value, current.next)
+          current.next = new_node
+          return
+        end
+        current = current.next
+      end
+      self.last(value)
     end
 
     # Helper method for tests
@@ -129,3 +300,24 @@ def create_cycle
       current.next = @head # make the last node link to first node
     end
 end
+
+# def has_cycle
+# fast = @head.next
+# fast = fast.next if fast
+# slow = @head
+
+# until fast.nil? || slow.nil
+#   if fast == slow
+#     return true
+#   end
+#   fast = fast.next
+#   return true if fast == slow
+#   fast = fast.next unless fast.nil?
+#   slow = slow.next
+# end
+# end
+
+
+
+
+

test/linked_list_test.rb

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