Leaves - Nicky C.

lib/linked_list.rb

@@ -1,4 +1,4 @@
-require_relative 'node'
+require_relative "node"
 
 class LinkedList
   attr_reader :head
@@ -7,39 +7,70 @@ 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 @head if @head.nil?
 
+    return @head.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) n is the size of the list
+  # Space complexity - O(1)
   def length
-    return 0
+    count = 0
+    current = head
+    until current.nil?
+      count += 1
+      current = current.next
+    end
+    return count
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) n is the length of the list
+  # Space complexity - O(1)
   def add_last(data)
-
+    if !@head
+      @head = Node.new(data)
+    else
+      current = @head
+      while current.next
+        current = current.next
+      end
+      current.next = Node.new(data)
+    end
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) where n is the length of the list
+  # Space complexity - O(1)
   def get_last
+    return nil unless @head
+    current = @head
 
+    while current.next
+      current = current.next
+    end
+
+    return current.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) where n is the index
+  # Space complexity - O(1)
   def get_at_index(index)
+    return nil unless @head
+
+    current = @head
 
+    index.times do
+      return nil unless current.next
+      current = current.next
+    end
+    return current.data
   end
 end

test/linked_list_test.rb

@@ -1,9 +1,8 @@
-require 'minitest/autorun'
-require 'minitest/reporters'
+require "minitest/autorun"
+require "minitest/reporters"
 require "minitest/skip_dsl"
 
-require_relative '../lib/linked_list'
-
+require_relative "../lib/linked_list"
 
 Minitest::Reporters.use! Minitest::Reporters::SpecReporter.new
 
@@ -13,24 +12,24 @@
     @list = LinkedList.new
   end
 
-  describe 'initialize' do
-    it 'can be created' do
+  describe "initialize" do
+    it "can be created" do
 
       # Assert
       expect(@list).must_be_kind_of LinkedList
     end
   end
 
-  xdescribe 'add_first & get_first' do
-    it 'can add values to an empty list' do
+  describe "add_first & get_first" do
+    it "can add values to an empty list" do
       # Act
-        @list.add_first(3)
+      @list.add_first(3)
 
-        # Assert
-        expect(@list.get_first).must_equal 3
+      # Assert
+      expect(@list.get_first).must_equal 3
     end
 
-    it 'will put the last added item to the front of the list' do
+    it "will put the last added item to the front of the list" do
       # Act
       @list.add_first(1)
       @list.add_first(2)
@@ -45,13 +44,12 @@
       expect(@list.get_first).must_equal 3
     end
 
-    it 'will return `nil` for `getFirst` if the list is empty' do
-
+    it "will return `nil` for `getFirst` if the list is empty" do
       expect(@list.get_first).must_be_nil
     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 +64,7 @@
     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
@@ -86,17 +84,15 @@
       expect(@list.get_first).must_equal 2
       expect(@list.get_last).must_equal 4
       expect(@list.length).must_equal 3
-
     end
-
   end
 
-  xdescribe 'get_at_index' do
-    it 'returns nil if the index is outside the bounds of the list' 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
 
-    it 'can retrieve an item at an index in the list' do
+    it "can retrieve an item at an index in the list" do
       @list.add_first(1)
       @list.add_first(2)
       @list.add_first(3)