water-marj

.gitignore

@@ -48,3 +48,6 @@ build-iPhoneSimulator/
 
 # unless supporting rvm < 1.11.0 or doing something fancy, ignore this:
 .rvmrc
+
+
+.idea/

lib/linked_list.rb

@@ -7,39 +7,83 @@ def initialize
     @head = nil
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - 1
+  # Space complexity - 1
   def add_first(data)
+    new_node = Node.new(data)
 
+    if @head.nil?
+      @head = new_node
+    else
+      new_node.next = @head
+      @head = new_node
+    end
+    return @head.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - 1
+  # Space complexity - 1
   def get_first
-
+    return @head.nil? ? @head : @head.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - n
+  # Space complexity - 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 - 1
+  # Space complexity - 1
   def add_last(data)
+    new_node = Node.new(data)
+    current = @head
+
+    if current.nil?
+      @head = new_node
+      return @head
+    else
+      while current.next != nil
+        current = current.next
+      end
+      current.next = new_node
+    end
 
+    return new_node
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - n
+  # Space complexity - 1
   def get_last
+    return nil if @head.nil?
+    count = 0
+    current = @head
 
+    while current.next != nil
+      count += 1
+      current = current.next
+    end
+    return current.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - n
+  # Space complexity - 1
   def get_at_index(index)
+    count = 0
+    current = @head
 
+    while count != index
+      count += 1
+      return nil if current.nil?
+      current = current.next
+    end
+    return current.data
   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