diff --git a/lib/linked_list.rb b/lib/linked_list.rb index 9e97557..517e681 100644 --- a/lib/linked_list.rb +++ b/lib/linked_list.rb @@ -7,39 +7,44 @@ def initialize @head = nil end - # Time complexity - ? - # Space complexity - ? + # Time complexity - O(1) + # Space complexity - O(n) 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 - + @head&.data end - # Time complexity - ? - # Space complexity - ? - def length - return 0 + # Time complexity - O(n) + # Space complexity - O(n) + def length(node=@head, len=0) + return len unless node + return length(node.next, len.succ) end - # Time complexity - ? - # Space complexity - ? - def add_last(data) - + # Time complexity - O(n) + # Space complexity - O(n) + def add_last(data, node=@head) + return add_first(data) unless node + return node.next = Node.new(data) unless node.next + return add_last(data, node.next) end - # Time complexity - ? - # Space complexity - ? - def get_last - + # Time complexity - O(n) + # Space complexity - O(n) + def get_last(node=@head) + return node&.data unless node&.next + return get_last(node.next) end - # Time complexity - ? - # Space complexity - ? - def get_at_index(index) - + # Time complexity - O(index) + # Space complexity - O(index) + def get_at_index(index, node=@head) + return node&.data unless node&.next && index > 0 + return get_at_index(index.pred, node.next) end end diff --git a/test/linked_list_test.rb b/test/linked_list_test.rb index 2a805c7..fac4c41 100644 --- a/test/linked_list_test.rb +++ b/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