Fire 🔥 - Aimee 👾

.rakeTasks

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Settings><!--This file was automatically generated by Ruby plugin.
+You are allowed to: 
+1. Remove rake task
+2. Add existing rake tasks
+To add existing rake tasks automatically delete this file and reload the project.
+--><RakeGroup description="" fullCmd="" taksId="rake"><RakeTask description="Run tests" fullCmd="test" taksId="test" /><RakeTask description="" fullCmd="default" taksId="default" /></RakeGroup></Settings>

Gemfile.lock

@@ -0,0 +1,36 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ansi (1.5.0)
+    builder (3.2.4)
+    coderay (1.1.3)
+    method_source (1.0.0)
+    minitest (5.14.2)
+    minitest-reporters (1.4.2)
+      ansi
+      builder
+      minitest (>= 5.0)
+      ruby-progressbar
+    minitest-skip (0.0.3)
+      minitest (~> 5.0)
+    minitest-spec (0.0.2.1)
+      minitest (>= 3.0)
+    pry (0.13.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    rake (13.0.1)
+    ruby-progressbar (1.10.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  minitest
+  minitest-reporters
+  minitest-skip
+  minitest-spec
+  pry
+  rake
+
+BUNDLED WITH
+   2.1.4

lib/linked_list.rb

@@ -1,4 +1,6 @@
 require_relative 'node'
+# helpful resource I used to work on this:
+# https://hackernoon.com/implementing-singly-linked-list-with-ruby-om2df3ya6
 
 class LinkedList
   attr_reader :head
@@ -7,39 +9,64 @@ def initialize
     @head = nil
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1) - A node is added to the beginning of the list. Since this is not an array, we are not replacing an element and shifting the rest of the data over.
+  # Space complexity - O(1)
   def add_first(data)
-
+    new_node = Node.new(data)
+    new_node.next = @head
+    @head = new_node
+    return @head
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(1) - We look up the first node (where the head is)
+  # Space complexity - O(1)
   def get_first
-
+    return @head.data unless @head.nil?
+    return nil
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) we count n nodes in 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) - need to traverse list of length n to find the last node and add one after that
+  # Space complexity - O(1)
   def add_last(data)
+    return add_first(data) if @head.nil?
 
+    current = @head
+    current = current.next until current.next.nil?
+
+    current.next = Node.new(data)
+    return current.next
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) - we need to traverse the list of length n to find the last node
+  # Space complexity - O(1)
   def get_last
-
+    return nil if @head.nil?
+    current = @head
+    current = current.next until current.next.nil?
+    return current.data
   end
 
-  # Time complexity - ?
-  # Space complexity - ?
+  # Time complexity - O(n) - worst case scenario, we need to iterate through n times to find the node (not a direct look up)
+  # Space complexity - O(1)
   def get_at_index(index)
-
+    return nil if @head.nil?
+    current = @head
+    index.times do
+      current = current.next
+    end
+    return current.data
   end
 end

lib/node.rb

@@ -3,8 +3,8 @@ class Node
   attr_reader :data
   attr_accessor :next
 
-  def initialize(value, nextNode = nil)
+  def initialize(value, next_node = nil)
     @data = value
-    @next = nextNode
+    @next = next_node
   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