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