60 lines
2.3 KiB
Markdown
60 lines
2.3 KiB
Markdown
## \-\-- Day 2: I Was Told There Would Be No Math \-\--
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The elves are running low on wrapping paper, and so they need to submit
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an order for more. They have a list of the dimensions (length `l`, width
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`w`, and height `h`) of each present, and only want to order exactly as
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much as they need.
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Fortunately, every present is a box (a perfect [right rectangular
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prism](https://en.wikipedia.org/wiki/Cuboid#Rectangular_cuboid)), which
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makes calculating the required wrapping paper for each gift a little
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easier: find the surface area of the box, which is
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`2*l*w + 2*w*h + 2*h*l`. The elves also need a little extra paper for
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each present: the area of the smallest side.
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For example:
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- A present with dimensions `2x3x4` requires `2*6 + 2*12 + 2*8 = 52`
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square feet of wrapping paper plus `6` square feet of slack, for a
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total of `58` square feet.
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- A present with dimensions `1x1x10` requires `2*1 + 2*10 + 2*10 = 42`
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square feet of wrapping paper plus `1` square foot of slack, for a
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total of `43` square feet.
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All numbers in the elves\' list are in
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feet.
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How many total *square feet of wrapping paper* should they order?
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## \-\-- Part Two \-\-- {#part2}
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The elves are also running low on ribbon. Ribbon is all the same width,
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so they only have to worry about the length they need to order, which
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they would again like to be exact.
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The ribbon required to wrap a present is the shortest distance around
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its sides, or the smallest perimeter of any one face. Each present also
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requires a bow made out of ribbon as well; the feet of ribbon required
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for the perfect bow is equal to the cubic feet of volume of the present.
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Don\'t ask how they tie the bow, though; they\'ll never tell.
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For example:
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- A present with dimensions `2x3x4` requires `2+2+3+3 = 10` feet of
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ribbon to wrap the present plus `2*3*4 = 24` feet of ribbon for the
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bow, for a total of `34` feet.
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- A present with dimensions `1x1x10` requires `1+1+1+1 = 4` feet of
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ribbon to wrap the present plus `1*1*10 = 10` feet of ribbon for the
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bow, for a total of `14` feet.
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How many total *feet of ribbon* should they order?
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Both parts of this puzzle are complete! They provide two gold stars:
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\*\*
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At this point, you should [return to your Advent calendar](/2015) and
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try another puzzle.
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If you still want to see it, you can [get your puzzle
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input](2/input).
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