Question

You need to write a while loop that continues until an integer x is in the set {2,3,4,5}. How would the loop be controlled?

A) while (x > 2 && x < 5)
B) while (x > 2 || x < 5)
C) while (x < 2 && x > 5)
D) while (x < 2 || x > 5)

Answer 1

why it's not A) and why it is B) ?

Answer 2

It is not A because the loop would break as soon as it crossed the threshold of 2 or 5, depending on which way it was going, this would cause the set to never include 3 or 4. Only by adding the OR as with B are you able to include all values between your bounds.

Answer 3

It's not B, it's actually D.

if you want a loop to continue, the boolean expression has to evaluate to true.

so if x = 1 which of them would be true?

A. 1 > 2 && 1 < 5 | false
B. 1 > 2 || 1 < 5 | true
C. 1 < 2 && 1 > 5 | false
D. 1 < 2 || 1 > 5 | true

Now it's either B or D
if x = 2
B would be true (this is not what you want)
D would be false (this seems to be what you want)

you can think about some more values of x but D is correct

Answer 4

yea....it's D

Answer 5

can you give me example why it is not C?

Answer 6

like above, if x = 1
C. 1 < 2 && 1 > 5 | false

it would need to be true for it to work

Answer 7

ok catch it....thnks

Answer 8

My bad, I read it as you wanted to continue "while" x was within the set and not "until".

Answer 9

me too