Stacks and Queues

A stack is

• interface

• class

• abstract class

A queue is

• interface

• class

• abstract class

How do you access the first element in the stack?

• stack.pop()

• stack.poll()

• stack.element()

• stack.peek()

How do you access the first element in a queue?

• queue.pop()

• queue.poll()

• queue.element()

• queue.peek()

What does the stack look like after the code runs? [bottom --> top]

• [12, 9, 6, 3, 0]

• [0, 3, 6, 9, 12, 16, 21]

• [0, 3, 6, 9, 12]

• [21, 16, 12, 9, 6, 3, 0]

What is printed after the code runs?

• [8, 16, 3, 7]

• [7, 3, 1, 2, 4, 8]

• [2, 4, 8, 16, 3, 7]

• [4, 16, 3, 7]

What is the prefix expression for the following infix expression: A + (B * C)

• A B C * +

• + A * B C

• + * A B C

• * + A B C

What is the postfix expression for the following infix expression:

(A + (B * C)) / (D - E)

• A B C D E * + - /

• A B C * + D E -­ /

• / + A * B C -­ D E

What is the infix for the following prefix expression: * + A B + C E

• (A + B) * (C + E)

• (A * B) + (C + E)

• (A + B) + (C * E)

What is one of the main differences between a stack and a queue/

• Queue: FIFO, Stack: LIFO

• Queue: LIFO, Stack: FIFO