Core IT Interview Questions?

Aengus asks: "We have a round of job interviews coming up and the people we will be interviewing will be of different backgrounds, so we are looking for a core set of general questions that you could apply to any IT/CS candidate that would display that they knew what they were talking about. ie questions that are not language or job specific. So far all we have come up with 'What algorithm is your favourite or most commonly used?'....." What questions have you been asked on interviews you have participated in?

Comments

Re:How do you think?

[Papineau]

Warning: try to answer yourself before reading the rest of this comment.

1) (Never saw those at a bank or elsewhere, but I think I can still figure out how they're made) So you need to be able to express all the numbers from 1 to 31, with 12 cube faces. You need 10 faces for 0 ,1, ... 8, 9. Then you need an extra 1, 2 and 3 for the tens. Which gives 13 faces, right? Wrong! You don't need two 3, as 33 is not a day of a month.
Now how to distribute those 12 symbols on the 2 cubes: You need both 1 and both 2 on different cubes (obviously). The rest can then be spread anyway you want, even though there's probably a way which minimizes the number of cube switching during the month.
Or, if you always want to show both cubes (which the previous answer didn't do), all you need is the 6 and the 9 to the inverse of each other. Then, cube A has 0, 1, 2, 3, 4, 5 and cube B has 0, 1, 2, 6, 7, 8 (with the 9 being an inverted 6).

2) I'd say 2 times, assuming you know the initial state of the lights, 3 times otherwise.
If you know the initial state, flip 2 switches, then see which lights have changed state. The one which didn't is the one connected to the switch you didn't use. Then reflip one of the 2 switches you started with. The light which has now changed state is connected to it, so the 3rd light and the 3rd switch are connected.
If you don't know the initial state, there's no purpose to flip some switches randomly and then enter the room, so enter and look at the state of the lights. Then do as above.

3) Build the dome on top of a flat roof with a round hole in the middle which connects the dome's base to the squared walls. Or if you don't care about the weather and/or the sun, make the diameter of your dome the same as the length of the walls: it will rest on the middle of each wall.

My turn:
1) How do you form 4 equal triangles with 6 matches? You can only connect the matches at their ends.
2) How do you cut a cake in 8 equal parts with only 3 cuts?
3) Assuming that with the previous question, not everybody had the same amount of topping, how do you cut the cake in 8 equal parts (topping included) with only 3 cuts?

Those were fun to do: do you have more?