35 lines
1.3 KiB
Markdown
35 lines
1.3 KiB
Markdown
## \-\-- Day 4: The Ideal Stocking Stuffer \-\--
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Santa needs help [mining](https://en.wikipedia.org/wiki/Bitcoin#Mining)
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some AdventCoins (very similar
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to [bitcoins](https://en.wikipedia.org/wiki/Bitcoin)) to use as gifts
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for all the economically forward-thinking little girls and boys.
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To do this, he needs to find [MD5](https://en.wikipedia.org/wiki/MD5)
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hashes which, in
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[hexadecimal](https://en.wikipedia.org/wiki/Hexadecimal), start with at
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least *five zeroes*. The input to the MD5 hash is some secret key (your
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puzzle input, given below) followed by a number in decimal. To mine
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AdventCoins, you must find Santa the lowest positive number (no leading
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zeroes: `1`, `2`, `3`, \...) that produces such a hash.
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For example:
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- If your secret key is `abcdef`, the answer is `609043`, because the
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MD5 hash of `abcdef609043` starts with five zeroes
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(`000001dbbfa...`), and it is the lowest such number to do so.
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- If your secret key is `pqrstuv`, the lowest number it combines with
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to make an MD5 hash starting with five zeroes is `1048970`; that is,
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the MD5 hash of `pqrstuv1048970` looks like `000006136ef...`.
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## \-\-- Part Two \-\-- {#part2}
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Now find one that starts with *six zeroes*.
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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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