Branches - Monick

lib/linked_list.rb

@@ -1,45 +1,82 @@
 require_relative 'node'
 
 class LinkedList
-  attr_reader :head
+  attr_reader :head, :tail
 
   def initialize
     @head = nil
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1) 
+  # Space complexity - O(1)
   def add_first(data)
-
+    @head = Node.new(data, head)
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1)
+  # Space complexity - O(1)
   def get_first
-
+    return nil if head.nil? 
+    return @head.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n)
+  # Space complexity - O(1)
   def length
-    return 0
+    count = 0 
+    return count if head.nil?
+
+    current = head 
+    until current.nil?
+      current = current.next
+      count += 1 
+    end 
+
+    return count 
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n)
+  # Space complexity - O(1)
   def add_last(data)
-
+    if head.nil?
+      @head = Node.new(data, nil)
+    else 
+      current = head 
+      while !current.next.nil?
+        current = current.next
+      end 
+
+      current.next = Node.new(data, nil)
+    end 
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n)
+  # Space complexity - O(1)
   def get_last
+    return nil if head.nil?
 
+    current = head 
+
+    until current.next.nil?
+      current = current.next
+    end 
+
+    return current.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n)
+  # Space complexity - O(1)
   def get_at_index(index)
+    return nil if head.nil?
+
+    current = head 
+    count = 0 
+
+    until count == index 
+      current = current.next 
+      count += 1
+    end 
 
+    return current.data
   end
 end

lib/node.rb

@@ -1,7 +1,7 @@
 # defines a node in a linkedList
 class Node
   attr_reader :data
-  attr_accessor :next
+  attr_accessor :next 
 
   def initialize(value, nextNode = nil)
     @data = value

test/linked_list_test.rb

@@ -21,7 +21,7 @@
     end
   end
 
-  xdescribe 'add_first & get_first' do
+  describe 'add_first & get_first' do
     it 'can add values to an empty list' do
       # Act
         @list.add_first(3)
@@ -51,7 +51,7 @@
     end
   end
 
-  xdescribe "length" do
+  describe "length" do
     it "will return 0 for an empty list" do
       expect(@list.length).must_equal 0
     end
@@ -66,7 +66,7 @@
     end
   end
 
-  xdescribe "addLast & getLast" do
+  describe "addLast & getLast" do
     it "will add to the front if the list is empty" do
       @list.add_last(1)
       expect(@list.get_first).must_equal 1
@@ -91,7 +91,7 @@
 
   end
 
-  xdescribe 'get_at_index' do
+  describe 'get_at_index' do
     it 'returns nil if the index is outside the bounds of the list' do
       expect(@list.get_at_index(3)).must_be_nil
     end