Blaine-fire

lib/linked_list.rb

@@ -7,39 +7,77 @@ def initialize
     @head = nil
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1)
+  # Space complexity - O(1)
   def add_first(data)
-
+  # current = Node.new(data, @head)
+  #   @head = current
+  # READ RIGHT TO LEFT 
+    @head = Node.new(data, @head)
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1)
+  # Space complexity - O(1)
   def get_first
-
+    if @head == nil
+      return nil
+    end
+    return @head.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1)
+  # Space complexity - O(1)
   def length
-    return 0
+    count = 0
+    current = @head
+    while current != nil
+      count += 1
+      current = current.next
+    end
+    return count
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1)
+  # Space complexity - O(1)
   def add_last(data)
-
+    if @head == nil
+      return add_first(data)
+    end
+    current = @head
+    until current.next == nil
+      current = current.next
+    end 
+    current.next = Node.new(data, nil)
+  # Get to the nod before nil
+  # current.next = nil
   end
 
   # Time complexity - ?
   # Space complexity - ?
   def get_last
-
+    current = @head
+    if current == nil
+      return nil
+    end
+    while current.next != nil
+      current = current.next
+    end
+    return current.data
   end
 
   # Time complexity - ?
   # Space complexity - ?
-  def get_at_index(index)
-
+  def get_at_index(index) 
+    count = 0
+    current = @head
+    while current != nil && count < index
+      count += 1
+      current = current.next
+    end
+    if current == nil
+      return nil
+    else
+      return current.data
+    end
   end
 end

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
@@ -93,7 +93,7 @@
     end
   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