2016-12-20 17:05:43 +00:00
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Advent of Code
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--- Day 20: Firewall Rules ---
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2018-03-15 16:24:23 +00:00
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You'd like to set up a small hidden computer here so you can use it to get
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back into the network later. However, the corporate firewall only allows
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communication with certain external IP addresses.
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2016-12-20 17:05:43 +00:00
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2018-03-15 16:24:23 +00:00
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You've retrieved the list of blocked IPs from the firewall, but the list
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seems to be messy and poorly maintained, and it's not clear which IPs are
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allowed. Also, rather than being written in dot-decimal notation, they are
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written as plain 32-bit integers, which can have any value from 0 through
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4294967295, inclusive.
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2016-12-20 17:05:43 +00:00
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2018-03-15 16:24:23 +00:00
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For example, suppose only the values 0 through 9 were valid, and that you
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retrieved the following blacklist:
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2016-12-20 17:05:43 +00:00
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5-8
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0-2
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4-7
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2018-03-15 16:24:23 +00:00
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The blacklist specifies ranges of IPs (inclusive of both the start and end
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value) that are not allowed. Then, the only IPs that this firewall allows
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are 3 and 9, since those are the only numbers not in any range.
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2016-12-20 17:05:43 +00:00
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2018-03-15 16:24:23 +00:00
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Given the list of blocked IPs you retrieved from the firewall (your puzzle
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input), what is the lowest-valued IP that is not blocked?
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2016-12-20 17:05:43 +00:00
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2018-03-15 16:24:23 +00:00
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Your puzzle answer was 31053880.
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2016-12-20 17:05:43 +00:00
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--- Part Two ---
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How many IPs are allowed by the blacklist?
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2018-03-15 16:24:23 +00:00
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Your puzzle answer was 117.
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2016-12-20 17:05:43 +00:00
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2016/about
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. http://adventofcode.com/2016/support
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. http://adventofcode.com/2016/events
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. http://adventofcode.com/2016/settings
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. http://adventofcode.com/2016/auth/logout
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/leaderboard
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. http://adventofcode.com/2016/stats
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. http://adventofcode.com/2016/sponsors
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. http://adventofcode.com/2016/sponsors
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. https://en.wikipedia.org/wiki/IPv4#Addressing
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. https://en.wikipedia.org/wiki/Dot-decimal_notation
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. https://en.wikipedia.org/wiki/32-bit
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/day/20/input
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