2015/advent23.sh

   1 count=0
   2 while read line; do
   3     inst[$((count++))]=$line
   4 done
   5 echo "read $count instructions, starting execution"
   6 a=0 b=0 pc=0 count=0
   7 [[ ! $part1 ]] && a=1
   8 while [[ ${inst[pc]+set} ]]; do
   9     : $((count++))
  10     read i r o <<< "${inst[pc]}"
  11     case $i in
  12         hlf) case $r in a) a=$((a/2));; b) b=$((b/2));; *) exit 2;; esac
  13              pc=$((pc+1)) ;;
  14         tpl) case $r in a) a=$((a*3));; b) b=$((b*3));; *) exit 2;; esac
  15              pc=$((pc+1)) ;;
  16         inc) case $r in a) a=$((a+1));; b) b=$((b+1));; *) exit 2;; esac
  17              pc=$((pc+1)) ;;
  18         jmp) pc=$((pc+r)) ;;
  19         jie) case $r in a,) ((a%2));; b,) ((b%2));; *) exit 2;; esac
  20              pc=$((pc+($? ? o : 1))) ;;
  21         jio) case $r in a,) ((a==1));; b,) ((b==1));; *) exit 2;; esac
  22              pc=$((pc+($? ? 1 : o))) ;;
  23         *) echo "invalid instruction $i, exiting"; exit 1 ;;
  24     esac
  25 done
  26 echo "final register state a=$a b=$b, after $count instructions executed"