day14/poly.sh

   1 #!/bin/bash
   2
   3 set -u
   4
   5 filename="${1:-example.txt}"
   6 exec 3<"$filename"
   7
   8 read -u 3 template
   9
  10 read -u 3 blank
  11
  12 declare -A inserts=()
  13
  14 declare -a results=($template)
  15
  16 while read -u 3 poly; do
  17     left="${poly% -> *}"
  18     right="${poly#* -> }"
  19     inserts[$left]="$right"
  20 done
  21
  22 for (( a=1; a<=10; a++ )); do
  23     cur_string="${results[$(($a-1))]}"
  24     for (( b=0; b<$((${#cur_string} - 1)); b++ )); do
  25         lookup="${cur_string:$b:2}"
  26         if [ $b -eq 0 ]; then
  27             results[$a]="${lookup:0:1}${inserts[$lookup]}"
  28         else
  29             results[$a]+="${lookup:0:1}${inserts[$lookup]}"
  30         fi
  31     done
  32     results[$a]+="${cur_string: -1:1}"
  33 done
  34
  35 declare -A counts
  36
  37 do_counts() {
  38     local string="$1"
  39     counts=()
  40
  41     for (( a=0; a<${#string}; a++ )); do
  42         char=${string:$a:1}
  43         if [ "${counts[$char]+abc}" ]; then
  44             ((counts[$char]+=1))
  45         else
  46             counts[$char]=1
  47         fi
  48     done
  49 }
  50
  51 get_highest_lowest() {
  52     local -n __results="$1"
  53     lowest_count=-1
  54     lowest_letter=""
  55     highest_count=-1
  56     highest_letter=""
  57     for key in "${!counts[@]}"; do
  58         if [ $lowest_count -eq -1 ]; then
  59             lowest_count=${counts[$key]}
  60             lowest_letter=$key
  61         elif [ ${counts[$key]} -lt $lowest_count ]; then
  62             lowest_count=${counts[$key]}
  63             lowest_letter=$key
  64         fi
  65         if [ $highest_count -eq -1 ]; then
  66             highest_count=${counts[$key]}
  67             highest_letter=$key
  68         elif [ ${counts[$key]} -gt $highest_count ]; then
  69             highest_count=${counts[$key]}
  70             highest_letter=$key
  71         fi
  72     done
  73
  74     __results[$lowest_count]=$lowest_letter
  75     __results[$highest_count]=$highest_letter
  76 }
  77
  78 do_counts "${results[-1]}"
  79 declare -a result_counts=()
  80 get_highest_lowest result_counts
  81
  82 declare -a temp=( "${!result_counts[@]}" )
  83 echo -n "Part 1: Difference between highest and lowest count: "
  84 echo $(("${temp[1]}" - "${temp[0]}"))