Fun C++ Problem

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Originally Posted by JasonD

I really need to point out that such a puzzle is a bad interview question. Such puzzles are fun, but they are not a good indication of programming ability. More importantly, as Joel Spolsky says it, it doesn't show if the candidate is smart and gets things done.

The puzzles are fun, no doubt. I love them. Just don't judge people based on how quickly they can solve it...

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Well put. I couldn't agree with you more.;)

Yes, it's a strange interview question.

I found the first solution in the first minute, then I thought 'what a pointless exercise' and went off and did something more interesting instead. ;)

I finally got all three! I'll admit that it helped when the details of the problem were explained... as it hinted at where I should look for the third solution (which was -i<n for me).

Three, it is very tricky question

new here, found this fun problem through google.

i+n was definitely the hardest one! remembering that the loop condition is only false when negative helped =)

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Originally Posted by pinchharmonic

i+n was definitely the hardest one! remembering that the loop condition is only false when negative helped =)

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Congratulations that you found it (which I didn't :o), but the loop condition is only false when zero! ;)

Ah, and: Welcome to CG! :)

What about

int i, n =-20;

?

Took about 5 minutes. I never would have thought of n+1. More than 3 solutions, I guess. : )

Got all three. Surprisingly I don't think the third solution took me as long as the second solution. :blush:

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Originally Posted by whitevandal

What about

int i, n =-20;

?

Took about 5 minutes. I never would have thought of n+1. More than 3 solutions, I guess. : )

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If n is -20, i=0 will never be less than n.
Interestingly, since I didn’t want to read past the first few posts, I did not realize that I played this game five years ago, and accidentally found (again) all three solutions. Again without timing; about 10 minutes, I guess.
Do I get a double bonus?

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Originally Posted by VladimirF

If n is -20, i=0 will never be less than n.
Interestingly, since I didn’t want to read past the first few posts, I did not realize that I played this game five years ago, and accidentally found (again) all three solutions. Again without timing; about 10 minutes, I guess.
Do I get a double bonus?

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i is DEcremented, not INcremented. So i will= -1, -2, -3...etc until it passes -20.

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Originally Posted by whitevandal

i is DEcremented, not INcremented. So i will= -1, -2, -3...etc until it passes -20.

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Right, but if n = -20

Then i < n will fail as 0 < -20 evaluates to false. Thus i will actually just equal 0, and "x" will be printing 0 times.

There are four so far... anyone want to see them

for (i=0; i+n; i--)
for (i=0; i<n; n--)
for (i=0;-i<n; i--)
for (i=0;~i<n; i--)

Neat question, not a very good introduction. Once someone finds three, they think they are a genius. Did someone find another?
By the way, the unary NOT is replacing a space (" ") just like the negative symbol

My bad, dumb, should've read the posts about the unary operator. Silly oversight, great problem for the class.

What's wrong with this one?

for (i=40; i<n; i--)

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Originally Posted by shavarsh

What's wrong with this one?

for (i=40; i<n; i--)

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This is a character insertion and as such it's against the rules which only allow changing existing characters.

I'm not trying to be a smart ***, but this is not insertion?
for (i=0;-i<n; i--)

Or in this case, we substitute default-hidden '+' ?

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Originally Posted by shavarsh

I'm not trying to be a smart ***, but this is not insertion?
for (i=0;-i<n; i--)

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The original code has a space character where the minus sign now is - so it is replacing the space.

Don't mean to show off but it took maybe 20 seconds. I can't imagine no one has got that on his quiz or whatever since 1999 that's absurd.