Doing some C learnin'.

Also, reformatted all the problems.

2017/day23/problem

@@ -0,0 +1,82 @@
+Advent of Code
+
+--- Day 23: Coprocessor Conflagration ---
+
+   You decide to head directly to the CPU and fix the printer from there. As
+   you get close, you find an experimental coprocessor doing so much work that
+   the local programs are afraid it will halt and catch fire. This would cause
+   serious issues for the rest of the computer, so you head in and see what you
+   can do.
+
+   The code it's running seems to be a variant of the kind you saw recently on
+   that tablet. The general functionality seems very similar, but some of the
+   instructions are different:
+
+     • set X Y sets register X to the value of Y.
+
+     • sub X Y decreases register X by the value of Y.
+
+     • mul X Y sets register X to the result of multiplying the value contained
+       in register X by the value of Y.
+
+     • jnz X Y jumps with an offset of the value of Y, but only if the value of
+       X is not zero. (An offset of 2 skips the next instruction, an offset of -1
+       jumps to the previous instruction, and so on.)
+
+     Only the instructions listed above are used. The eight registers here,
+     named a through h, all start at 0.
+
+   The coprocessor is currently set to some kind of debug mode, which allows
+   for testing, but prevents it from doing any meaningful work.
+
+   If you run the program (your puzzle input), how many times is the mul
+   instruction invoked?
+
+   Your puzzle answer was 9409.
+
+--- Part Two ---
+
+   Now, it's time to fix the problem.
+
+   The debug mode switch is wired directly to register a. You flip the switch,
+   which makes register a now start at 1 when the program is executed.
+
+   Immediately, the coprocessor begins to overheat. Whoever wrote this program
+   obviously didn't choose a very efficient implementation. You'll need to
+   optimize the program if it has any hope of completing before Santa needs
+   that printer working.
+
+   The coprocessor's ultimate goal is to determine the final value left in
+   register h once the program completes. Technically, if it had that... it
+   wouldn't even need to run the program.
+
+   After setting register a to 1, if the program were to run to completion,
+   what value would be left in register h?
+
+   Your puzzle answer was 913.
+
+   Both parts of this puzzle are complete! They provide two gold stars: **
+
+   At this point, all that is left is for you to admire your advent calendar.
+
+   If you still want to see it, you can get your puzzle input.
+
+References
+
+   Visible links
+   . http://adventofcode.com/
+   . http://adventofcode.com/2017/about
+   . http://adventofcode.com/2017/support
+   . http://adventofcode.com/2017/events
+   . http://adventofcode.com/2017/settings
+   . http://adventofcode.com/2017/auth/logout
+   . http://adventofcode.com/2017
+   . http://adventofcode.com/2017
+   . http://adventofcode.com/2017/leaderboard
+   . http://adventofcode.com/2017/stats
+   . http://adventofcode.com/2017/sponsors
+   . http://adventofcode.com/2017/sponsors
+   . https://en.wikipedia.org/wiki/Halt_and_Catch_Fire
+   . http://adventofcode.com/2017/day/18
+   . http://adventofcode.com/2017
+   . http://adventofcode.com/2017/day/23/input