Leaves - Julia K #24

Kalakalot · 2019-12-07T22:42:17Z

Linked List Comprehension Questions

Question	Response
1. What advantages does a LinkedList have over an Array?	Adding to and removing from the front of list is more efficient -- O(1) as opposed to O(n) -- so inserting and deleting can be much faster. Linked lists are also more memory efficient since nodes don't have to be next to each other in memory.
2. When is an Array more advantageous?	Arrays seem much handier when efficiency isn't super important and you want to use built-in methods to transform data. Also, if you are accessing elements via index, lookup is a constant-time operation (unlike in linked lists, where index lookup is O(i) where i is the index.)
3. When is an ~~Array~~ Linked List more advantageous?	If you want to conserve memory and maximize time efficiency, linked lists are a better choice since you don't need contiguous memory space for each element, memory is assigned dynamically, deleting is almost always faster, and adding can also be much faster.

…ing sense so far.

…ast. Considered changing test names to snake case -- i.e. add_last instead of addLast -- but decided it's unnecessary in this situation. Glad to see I'm not the only one who mixes up Ruby and JavaScript conventions.

CheezItMan

Nice work, you hit the learning goals here. That said you have some inefficiencies here with how you used the length method in some of your solutions. Take a look at my comments and let me know what questions you have.

CheezItMan · 2019-12-18T05:44:42Z

lib/linked_list.rb

@@ -1,45 +1,95 @@
 require_relative 'node'
+require 'pry'


In the future please remove pry before submitting.

CheezItMan · 2019-12-18T05:44:52Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - O(1) because only one operation will be performed regardless of how many nodes the list has
+  # Space complexity - Also O(1)
  def add_first(data)


CheezItMan · 2019-12-18T05:44:59Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - Also O(1) because again, only one operation is being performed regardless of list length
+  # Space complexity - O(1)
  def get_first


CheezItMan · 2019-12-18T05:45:12Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - O(n) because we are performing an operation for every node in the list
+  # Space complexity - I think it's constant, because although we are assigning current and count variable values for each node in the list, we are overwriting existing variables instead of creating new variables each time, meaning we're just re-using the same places in memory. 
  def length


CheezItMan · 2019-12-18T05:45:34Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - O(n) because the only way we can get to the end of the list is by manually moving through each list node
+  # Space complexity - Constant because we are re-using the same variables instead of creating new variables for each node. 
  def add_last(data)


CheezItMan · 2019-12-18T05:46:29Z

lib/linked_list.rb

+    if length == 0
+      add_first(data)
+    else
+      # use length method to move to the last node in the list
+      (length - 1).times do 


Just note that since length is a method, you're calling it twice here, potentially, so this becomes a runtime of 3n instead of n. It doesn't change the Big-O, but it's a bit inefficient.

CheezItMan · 2019-12-18T05:47:05Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - Same as add_last
+  # Space complexity - Same as add_last
  def get_last


Similar issues with the above. Can you think of a simple way to make this more efficient?

CheezItMan · 2019-12-18T05:47:29Z

lib/linked_list.rb

+    # initialize current to head
+    current = @head
+    # account for index being greater than list length
+    if index + 1 > length


CheezItMan · 2019-12-18T05:47:34Z

lib/linked_list.rb

-  # Space complexity - ?
+
+  # Time complexity - O(i) where i is the index
+  # Space complexity - constant
  def get_at_index(index)


Julia A Kingrey added 5 commits December 7, 2019 12:41

Passing tests for add_first, get_first, and length. Everything is mak…

b72ff81

…ing sense so far.

Passing tests for add_last and get_last.

874c036

Passing all tests.

fe7c360

Passing all tests.

dca1811

CheezItMan reviewed Dec 18, 2019

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Leaves - Julia K #24

Leaves - Julia K #24

Kalakalot commented Dec 7, 2019

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Leaves - Julia K #24

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Leaves - Julia K #24

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Kalakalot commented Dec 7, 2019

Linked List Comprehension Questions

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