Shirley #24

shirley1chu · 2019-09-13T18:29:07Z

Stacks and Queues

Thanks for doing some brain yoga. You are now submitting this assignment!

Question	Answer
What is an ADT?	Abstract Data Type is agnostic about implementation details (such as whether an array or linked list is used to make a stack/queue), but is defined by the set of operations it can perform.
Describe a Stack	ADT with LIFO structure. The last item added is the first to get removed
What are the 5 methods in Stack and what does each do?	Push -> adds an element at top of the stack. Pop -> removes top element and returns the value. Is_empty -> boolean for whether stack is empty. Size -> returns length of stack. Peek -> returns top element value, but DOES NOT remove from stack.
Describe a Queue	ADT with FIFO structure. First element added is first to get removed.
What are the 5 methods in Queue and what does each do?	enqueue: adds element to back of queue dequeue: removes first element from q, returns element value is_empty? : boolean whether q is empty size: returns q length front: returns value of first element, but doesn't remove it
What is the difference between implementing something and using something?	Implement is creating something (writing a method) for use, and using is simply consuming it (calling a method).

Question	Answer
Did you include a sample run of your code as a comment?

CheezItMan

Nicely done. I like how you did the postfix exercise. You also did very well with the Queue and the circular buffer. Nice work!

CheezItMan · 2019-09-17T02:09:37Z

lib/problems.rb

@@ -1,9 +1,58 @@
-require_relative './stack.rb'
+require_relative "./stack.rb"

 def balanced(string)


CheezItMan · 2019-09-17T02:09:54Z

lib/problems.rb

+      return false unless pop_c && pop_c == char_map[c]
+    end
+  end
+  return stack.empty?
 end

 def evaluate_postfix(postfix_expression)


CheezItMan · 2019-09-17T02:11:07Z

lib/queue.rb

  end

  def front
-    raise NotImplementedError, "Not yet implemented"
+    return @head == -1 ? nil : store[@head]
  end

  def size


CheezItMan · 2019-09-17T02:11:28Z

lib/queue.rb

  end

  def to_s
-    return @store.to_s
+    clone_store = @store.clone
+    clone_store.delete(nil)


Chu added 6 commits September 12, 2019 11:59

stack tests passed

42b8f85

passed q tests

f88b5e8

string balance works!

b266f7f

added notes to balanced

692c437

all tests passed (finished postfix)

6938bdc

added circular buffer

a6442d3

CheezItMan reviewed Sep 17, 2019

View reviewed changes