Ch 3: Stacks, Queues, Exceptions, Templates

Question 1

what is a stack?

Answer 1

an ADT in which items are only inserted on or removed from the top of the stack

Question 2

what are the two operations of stacks and what do they do?

Answer 2

1. push: inserts an item on the top of the stack

2. pop: removes and returns the item at the top of the stack

Question 3

what is the acronym rule for stacks?

Answer 3

FILO- first in last out

Question 4

what does peek do for stacks?

Answer 4

returns but does not remove the item at the top of the stack

Question 5

does peek change the stack?

Answer 5

no, just returns the item at the top of the stack

Question 6

should peek and pop be called on an empty stack? why?

Answer 6

they should not be called on empty stacks because the behavior may be undefined

Question 7

what is a queue?

Answer 7

an ADT in which items are inserted at the end of the queue and removed from the front of the queue

Question 8

what are the two operations of queues and what do they do?

Answer 8

1. enqueue: insert an item at the end of the queue

2. dequeue: removes and returns the item at the front of the queue

Question 9

what is the acronym rule for queues?

Answer 9

FIFO - first in first out

Question 10

what is a deque (deck) ?

Answer 10

• an ADT in which items can be inserted and removed at both the front and back
• aka “double-ended” queue”

Question 11

what is an array-based list?

Answer 11

a list ADT implemented using an array

Question 12

what happens if there is no more room for objects in the array?

Answer 12

• array must be resized

- array size is doubled

Question 13

what is the Big O for resizing and why?

Answer 13

O(N) because it has to go through each item in the array and copy it to the new array

Question 14

what is the Big O for push back when there is no more room in an array and why?

Answer 14

• push back is O(1) because it always knows where the end of the list is
• having to resize is O(N)
• because you double the size when resizing, the impact of O(N) is minimal as it continues to do it, so, therefore, push back and having to resize is O(1)

Question 15

what is error-checking code?

Answer 15

code a programmer writes to detect and handle errors that occur during program execution

Question 16

what is an exception?

Answer 16

a circumstance that a program was not designed to handle

Question 17

what are exception-handling constructs?

Answer 17

• special constructs to keep error-checking code separate and to reduce redundant checks
• try, catch, throw

Question 18

what is the try block?

Answer 18

surrounds normal code, which is exited immediately if a throw statement executes

Question 19

what is a throw statement?

Answer 19

• appears within a try block; if reached, execution jumps immediately to the end of the try block
• written so only error situations lead to reaching a throw

Question 20

what is a catch clause?

Answer 20

• immediately follows a try block; if the catch was reached due to an exception of the catch clauses’ parameter type, the clause executes
• catches the thrown exception

Question 21

what is a handler?

Answer 21

catch block; handles the exception

Question 22

what is the point of try-catch?

Answer 22

• to simplify code

- so that code is not bombarded with endless if-statements checking for error

Question 23

do catch blocks have to follow try blocks?

Answer 23

yes

Question 24

explain try-catches in main & function

Answer 24

try block is in main, when it calls a function, the throw is in the function if it is in a situation that it doesn’t know how to handle. then the function ends and the throw is taken back to main and the catch is executed

Question 25

explain how throws and catches work for different types

Answer 25

throws can be for different types, therefore there are catches of different types

Question 26

what is “catch(…)”?

Answer 26

• a catch-all handler that catches any type

- useful when listed as the last handler

Question 27

should the catch-all ( catch(…)) be before the other catches?

Answer 27

no because the catches are run in order when the exception is thrown. since the catch-all is for last resorts, it should be called after the other handlers

Question 28

what is a function template?

Answer 28

a function definition having a special type parameter that may be used in place of types in the function

Question 29

what is a type parameter?

Answer 29

used through the function for any parameter types, return types or local variable types

Question 30

what is a class template?

Answer 30

a class definition having a special type parameter that may be used in place of type in the class

Question 31

what is the point of templates?

Answer 31

avoid writing and maintaining redundant classes that only differ by data type