Java Stacks Quiz

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Question Zero

What best describes the stack paradigm?

FIFO FILO

Which method inserts an element?

push() pop() isEmpty() peek()

Which method looks at the top element??

push() pop() isEmpty() peak()

Which method removes the top element?

push() pop() isEmpty() peak()

Which method checks if there are elements in the stack?

push() pop() isEmpty() peak()

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Question One

  public class StackTest{
    public static void main(String[] args){
      Stack<Integer> stack = new Stack<Integer>();
      
      for(int i = 0; i < 10; i++)
        stack.push(i);

      stack.pop();
      stack.pop();
      stack.pop();
    }
  }
  

What is the value returned when stack.peek() is called?

stack.peek()=

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Question Two

  public class StackTest{
    public static void main(String[] args){
      Stack<Integer> stackOne = new Stack<Integer>();
      Stack<Integer> stackTwo = new Stack<Integer>();
      
      for(int i =0; i<5; i++)
        stackOne.push(i);
      
      stackTwo.push(stackOne.pop());
      stackTwo.push(stackOne.pop());
      stackTwo.push(stackOne.pop());
    }
  }
  

What are the values returned by peeking on each stack?

stackOne.peek()=

stackTwo.peek()=

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Question Three

  public class Test{
    public static void main(String[] args){
      Stack<Integer> stack = new Stack<Integer>();
      int n = 12
      while (n > 0){
        stack.push(n%2);
        n = n/2;
      }
      String result = "";
      while (!stack.isEmpty())
        results += stack.pop();
      System.out.println(result)
    }
  }
  

What is printed out?

result=

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Question Four

  public class Test{
    public static void main(String[] args){
      Stack<Integer> stack = new Stack<Integer>();
      Scanner scanner = new Scanner(System.in)
      while (true){
        char ch = scanner.next();
        if(ch == '(')
          stack.push(1);
        else if (ch == ')' && !stack.isEmpty())
          stack.pop();
        else
          System.println("unbalanced");
      }
    }
  }
  

Which unbalanced input does this program consider correct?

(()()))
(()))()
((())
())(()

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Question Five

  public class Test{
    public static void main(String[] args){
      Stack<Integer> stackOne = new Stack<Integer>();
      Stack<Integer> stackTwo = new Stack<Integer>();
      for(int i = 0; i < 100; i++)
        stackOne.push(i);
      for(int i = 0; i < 100; i++)
        if(i%4==0)
          stackTwo.push(stackOne.peek());
      }
  }
  

How many elements are in each Stack?

stackOne size:

stackTwo size:

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Question Six

Which is something you would not use a stack for?

Reversing a word
Breadth First Search
Depth-First Search
backtracking (ie. edit->undo)

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Question Seven

How many calls to pop() is need to determine the size of a stack? Answer in terms of n where n is the number of elements in the stack.

n (linear)
nlog(n) (logarithmic)
n^x (polynomial)
x^n (exponential)

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Question Eight

Which data structures can easily represent a stack?
Choose all that apply.

Binary Tree
Linked List
Array
Queue

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Question Nine (Challenging - not tested)

Implement a stack with two queues

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Question Ten

Which Stack is more helpful?

https://stackexchange.com/
https://stackoverflow.com/

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