Advent of Code

--- Day 23: Opening the Turing Lock ---

   Little Jane Marie just got her very first computer for Christmas from some
   unknown benefactor. It comes with instructions and an example program, but
   the computer itself seems to be malfunctioning. She's curious what the
   program does, and would like you to help her run it.

   The manual explains that the computer supports two registers and six
   instructions (truly, it goes on to remind the reader, a state-of-the-art
   technology). The registers are named a and b, can hold any non-negative
   integer, and begin with a value of 0. The instructions are as follows:

     • hlf r sets register r to half its current value, then continues with the
       next instruction.

     • tpl r sets register r to triple its current value, then continues with
       the next instruction.

     • inc r increments register r, adding 1 to it, then continues with the
       next instruction.

     • jmp offset is a jump; it continues with the instruction offset away
       relative to itself.

     • jie r, offset is like jmp, but only jumps if register r is even ("jump
       if even").

     • jio r, offset is like jmp, but only jumps if register r is 1 ("jump if
       one", not odd).

   All three jump instructions work with an offset relative to that
   instruction. The offset is always written with a prefix + or - to indicate
   the direction of the jump (forward or backward, respectively). For example,
   jmp +1 would simply continue with the next instruction, while jmp +0 would
   continuously jump back to itself forever.

   The program exits when it tries to run an instruction beyond the ones
   defined.

   For example, this program sets a to 2, because the jio instruction causes it
   to skip the tpl instruction:

 inc a
 jio a, +2
 tpl a
 inc a

   What is the value in register b when the program in your puzzle input is
   finished executing?

   Your puzzle answer was 255.

   The first half of this puzzle is complete! It provides one gold star: *

--- Part Two ---

   The unknown benefactor is very thankful for releasi-- er, helping little
   Jane Marie with her computer. Definitely not to distract you, what is the
   value in register b after the program is finished executing if register a
   starts as 1 instead?

   Although it hasn't changed, you can still get your puzzle input.

   Answer: 334

References

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   . https://en.wikipedia.org/wiki/Processor_register
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   . https://en.wikipedia.org/wiki/Natural_number
   . http://adventofcode.com/day/23/input
