81 lines
2.8 KiB
Plaintext
81 lines
2.8 KiB
Plaintext
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
|
||
|
||
Visible links
|
||
. http://adventofcode.com/
|
||
. http://adventofcode.com/about
|
||
. http://adventofcode.com/stats
|
||
. http://adventofcode.com/leaderboard
|
||
. http://adventofcode.com/settings
|
||
. http://adventofcode.com/auth/logout
|
||
. https://en.wikipedia.org/wiki/Processor_register
|
||
. https://en.wikipedia.org/wiki/Instruction_set
|
||
. https://en.wikipedia.org/wiki/Natural_number
|
||
. http://adventofcode.com/day/23/input
|