Dani - Leaves

lib/linked_list.rb

@@ -19,54 +19,125 @@ 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
+      new_node = Node.new(value, @head)
+      @head = new_node 
     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
+      return false if @head == nil
+
+      current = @head
+      found = false
+      until current == nil
+        if current.data == value
+          found = true
+          break
+        end 
+
+        current = current.next
+      end
+      return found
     end
 
     # method to return the max value in the linked list
     # returns the data value and not the node
     def find_max
-      raise NotImplementedError
+      return nil if @head == nil
+
+      current = @head
+      max = current.data
+
+      until current == nil
+        if current.data > max
+          max = current.data
+        end
+        current = current.next
+      end
+      return max
     end
 
     # method to return the min value in the linked list
     # returns the data value and not the node
     def find_min
-      raise NotImplementedError
+      return nil if @head == nil
+
+      current = @head
+      min = 0
+      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
+      return 0 if @head == nil
+
+      current = @head
+      length = 0
+      until current == nil
+        length += 1
+        current = current.next
+      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
+
+      index.times do 
+        if current != nil
+          current = current.next
+        end
+      end
+
+      if current != nil
+        return  current.data
+      else
+        return nil
+      end
     end
 
     # method to print all the values in the linked list
     def visit
-      raise NotImplementedError
+      return nil if @head == nil
+      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
+      return nil if @head == nil
     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
+      return nil if @head == nil
+      current = @head
+      previous = nil
+
+      while current != nil
+        next_value = current.next  
+        current.next = previous
+        previous = current
+        current = next_value 
+      end
+
+      @head = previous
     end
 
 
@@ -79,7 +150,25 @@ def find_middle_value
     # 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
+      return nil if @head == nil
+
+      answer_pointer = @head
+      scanning_pointer = answer_pointer
+
+      n.times do 
+        if scanning_pointer.next != nil 
+          scanning_pointer = scanning_pointer.next
+        else
+          return nil
+        end
+      end
+
+      until scanning_pointer.next == nil
+        answer_pointer = answer_pointer.next
+        scanning_pointer = scanning_pointer.next
+      end
+
+      return answer_pointer.data
     end
 
     # checks if the linked list has a cycle. A cycle exists if any node in the
@@ -94,18 +183,41 @@ def has_cycle
     # returns the value in the first node
     # returns nil if the list is empty
     def get_first
-      raise NotImplementedError
+      if @head == nil
+        return @head
+      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
+      if @head == nil
+        add_first(value)
+      else
+        current = @head
+        previous = current
+        new_last_node = Node.new(value, nil)
+
+        until current.next == nil
+          current = current.next
+        end
+        current.next = new_last_node
+      end
     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 nil if @head == nil
+
+      current = @head
+
+      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
@@ -123,7 +235,7 @@ def create_cycle
       # navigate to last node
       current = @head
       while current.next != nil
-          current = current.next
+        current = current.next
       end
 
       current.next = @head # make the last node link to first node