Branches - Monick

lib/linked_list.rb

@@ -19,38 +19,88 @@ 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
+      return nil if @head.nil?
+      max = 0
+      current = @head
+
+      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?
+      min = nil 
+      current = @head
+
+      until current.nil? 
+        if min == nil 
+          min = current.data 
+        elsif 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
+      count = 0 
+      return count if @head.nil?
+
+      current = @head 
+      until current.nil?
+        current = current.next
+        count += 1 
+      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)
-      raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head 
+      count = 0 
+
+      until count == index 
+        current = current.next 
+        count += 1
+      end 
+
+      return current.data
     end
 
     # method to print all the values in the linked list
@@ -60,13 +110,40 @@ def visit
 
     # method to delete the first node found with specified value
     def delete(value)
-      raise NotImplementedError
+      return nil if @head.nil?
+
+      current = @head 
+      prev = nil
+
+      until current.data == value
+        prev = current 
+        current = current.next 
+      end
+
+      if prev.nil?
+        @head = current.next
+      else
+        prev.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
+      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
 
 
@@ -79,7 +156,23 @@ 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?
+      current = @head
+
+      length = 0 
+      until current.next.nil?
+        length += 1
+        current = current.next
+      end 
+
+      nth = @head
+      nth_length = length - n 
+      return nil if nth_length < 0 
+      nth_length.times do
+        nth = nth.next
+      end 
+
+      return nth.data 
     end
 
     # checks if the linked list has a cycle. A cycle exists if any node in the
@@ -94,18 +187,36 @@ def has_cycle
     # returns the value in the first node
     # returns nil if the list is empty
     def get_first
-      raise NotImplementedError
+      return nil if @head.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
+      if @head.nil?
+        @head = Node.new(value, nil)
+      else 
+        current = @head 
+        while !current.next.nil?
+          current = current.next
+        end 
+
+        current.next = Node.new(value, nil)
+      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