day5/get_seat_id.sh

   1 #!/bin/bash
   2
   3 parse_line() {
   4     line=$1
   5     row=${line:0:7}
   6     col=${line:7}
   7     row_number=$(row_part=${row//F/0}; row_part=${row_part//B/1}; echo $((2#$row_part)))
   8     col_number=$(col_part=${col//L/0}; col_part=${col_part//R/1}; echo $((2#$col_part)))
   9     seat_id=$((($row_number*8) + $col_number))
  10     echo "$seat_id,$row_number,$col_number"
  11 }
  12
  13 exec 3<input.txt
  14
  15 declare -A seats
  16
  17 while read -u 3 line; do
  18     data=$(parse_line $line)
  19     seat_id=${data%%,*}
  20     row_col=${data#*,}
  21     seats[$seat_id]=$row_col
  22 done
  23
  24 sorted_seats=( $(echo "${!seats[@]}" | tr ' ' '\n' | sort -g) )
  25
  26 echo Last seat id: ${sorted_seats[$((${#sorted_seats[@]}-1))]}
  27
  28 # find our seat by going through the sorted list and finding the first mismatch
  29 seat_num=${sorted_seats[0]}
  30 for seat in ${sorted_seats[@]}; do
  31     if [ $seat -ne $seat_num ]; then
  32         echo "Your seat number is: $seat_num"
  33         break
  34     fi
  35     seat_num=$((seat_num+1))
  36 done
  37
  38 exit 0
  39