Hacker News Reader

Comment by SilasX | Hacker News Reader

>Can you explain why you think it has two correct interpretations?

Because it depends on whether you 1) require that the N pieces be congruent and 2) what counts as a cut. I think the textbook answer is based on assuming 1) no, and 2) cutting along a line segment at least as long as a side.

Alternately, what counts as a "board" and a "cut".

Then you get the answer by assuming you cut a square board in half, then one of the pieces into squares (which requires cutting along a line segment half as long).

View on HN

Some people are arguing about whether 'cut into two' might really mean 'cut two off'. So I think your answer makes three interpretations (and nicely demonstrates that you do indeed have to specify things like "cutting is abstract and all cuts are of the same length").

The problem does specify 'works as fast' without any regard for length, though. And it obviously isn't actually a geometry problem because it doesn't even specify any ratios or angles - you could just cut a corner off and be done in a few seconds!

I agree with you here. If a board is 2 x 2 and you cut it in half, you have 2 1x2 pieces. That took 10 minutes. If you cut one of those 1x2 pieces in half you could have 2 1x1 pieces of board, and one 1x2 piece of board, thus 3 pieces. The first cut took 10 minutes, the 2nd cut, being half the size of the original took 5 minutes, thus 15 minutes.

Lumber has three dimensions.

I read 2x2 and thought,"that's not a board!" and wondered why s/he was cutting it lengthwise to get 1x2.

If it was dressed, that 1 might be very small indeed.

Like that:

  -------------
  |     |     |
  |     |     |
  |-----------|
  |           |
  |           |
  -------------

Or you could say 11 minutes and do this:

  -------------
  |/          |
  |           |
  |-----------|
  |           |
  |           |
  -------------

Cut into two equal pieces and then cut off the corner :)

There's a picture next to the question of a saw cutting a straight thin plank. Its very unlikely that this interpretation of the question was intended.

Reply on news.ycombinator.com