day15/memory.sh

   1 #!/bin/bash
   2
   3 set -u
   4
   5 read_file() {
   6     filename="$1"
   7     local IFS=","
   8     exec 3<"$filename"
   9     read -u 3 -a data
  10 }
  11
  12 get_answer() {
  13     local number=$1
  14     local count=$2
  15     if [ ${lastseen[$number]+a} ]; then
  16         answers[$count]=$((count-${lastseen[$number]}-1))
  17     else
  18         answers[$count]=0
  19     fi
  20 }
  21
  22 do_nothing() {
  23     return
  24 }
  25
  26 error_echo() {
  27     echo "$@" >&2
  28 }
  29
  30 DEBUG="${DEBUG:-}"
  31 debug_func=do_nothing
  32
  33 if [ -n "$DEBUG" ]; then
  34     debug_func="error_echo"
  35 fi
  36
  37 filename="${1:-p1_436.txt}"
  38
  39 read_file "$filename"
  40
  41 declare -A lastseen
  42 declare -a answers
  43
  44 current_answer=-1
  45 last_answer=-1
  46 count=0
  47
  48 for number in ${data[@]}; do
  49     count=$((count+1))
  50     last_answer=$current_answer
  51     if [ $last_answer -ge 0 ]; then
  52         lastseen[$last_answer]=$((count-1))
  53     fi
  54     answers[$count]=$number
  55     current_answer=$number
  56 done
  57
  58 while [ $count -lt 2020 ]; do
  59     count=$((count+1))
  60     get_answer $current_answer $count
  61     last_answer=$current_answer
  62     lastseen[$last_answer]=$((count-1))
  63     current_answer=${answers[$count]}
  64     $debug_func "$count: ${answers[$count]}"
  65 done
  66
  67 echo "Part 1: ${answers[$count]}"
  68
  69 while [ $count -lt 30000000 ]; do
  70     count=$((count+1))
  71     get_answer $current_answer $count
  72     last_answer=$current_answer
  73     lastseen[$last_answer]=$((count-1))
  74     current_answer=${answers[$count]}
  75     $debug_func "$count: ${answers[$count]}"
  76 done
  77
  78 echo "Part 2: ${answers[$count]}"