day13/fold.sh

   1 #!/bin/bash
   2
   3 set -u
   4
   5 declare -a points=()
   6 declare -a folds=()
   7
   8 filename="${1:-example.txt}"
   9 exec 3<"$filename"
  10
  11 max_x=0
  12 max_y=0
  13
  14 while read -u 3 line; do
  15     if [ "$line" == "" ]; then
  16         break
  17     fi
  18     x=${line%,*}
  19     y=${line#*,}
  20     if [ $x -gt $max_x ]; then
  21         max_x=$x
  22     fi
  23     if [ $y -gt $max_y ]; then
  24         max_y=$y
  25     fi
  26     points+=($line)
  27 done
  28
  29 ((max_x+=1))
  30 ((max_y+=1))
  31
  32 while read -u 3 line; do
  33     folds+=(${line#fold along })
  34 done
  35
  36 display_map() {
  37     for (( y=0; y<$max_y; y++ )); do
  38         for (( x=0; x<$max_x; x++ )); do
  39             offset=$(((y*$max_x) + $x))
  40             case "${map[$offset]}" in
  41                 0)
  42                     echo -n "."
  43                     ;;
  44                 1)
  45                     echo -n "#"
  46                     ;;
  47             esac
  48         done
  49         echo
  50     done
  51 }
  52
  53 declare -a map
  54
  55 # now build a map
  56 for (( a=0; a<$(($max_x * $max_y)); a++ )); do
  57     map[$a]=0
  58 done
  59
  60 for point in "${points[@]}"; do
  61     x=${point%,*}
  62     y=${point#*,}
  63     offset=$((($y*$max_x)+$x))
  64     map[$offset]=1
  65 done
  66
  67 fold() {
  68     local line="$1"
  69     local axis=${line%=*}
  70     local point=${line#*=}
  71     local dot="."
  72
  73     declare -a new_map=()
  74
  75     case $axis in
  76         x)
  77             local new_max_x=$(($max_x - $point - 1))
  78             if [ $point -gt $new_max_x ]; then
  79                 new_max_x=$point
  80             fi
  81             local adj=$((max_x % 2))
  82             for (( y=0; y<$max_y; y++ )); do
  83                 for (( x=0; x<$new_max_x; x++ )); do
  84                     x_1=$(($point - $new_max_x + $x))
  85                     x_2=$(($max_x - ($new_max_x - $point) - $x - $adj))
  86                     offset_1=$((($y * $max_x) + $x_1))
  87                     offset_2=$((($y * $max_x) + $x_2))
  88                     if [ $x_1 -lt 0 ]; then
  89                         offset_1=$offset_2
  90                     fi
  91                     if [ $x_2 -ge $max_x  ]; then
  92                         offset_2=$offset_1
  93                     fi
  94                     new_map+=($((${map[$offset_1]} | ${map[$offset_2]})))
  95                 done
  96             done
  97             map=("${new_map[@]}")
  98             max_x=$new_max_x
  99             ;;
 100         y)
 101             local new_max_y=$(($max_y - $point - 1))
 102             if [ $point -gt $new_max_y ]; then
 103                 new_max_y=$point
 104             fi
 105             local adj=$((max_y % 2))
 106             for (( y=0; y<$new_max_y; y++ )); do
 107                 # do the y offsets here
 108                 y_1=$(($point - $new_max_y + $y))
 109                 y_2=$(($max_y - ($new_max_y - $point) - $y - $adj))
 110                 offset_1=$(($y_1 * $max_x))
 111                 offset_2=$(($y_2 * $max_x))
 112                 if [ $y_1 -lt 0 ]; then
 113                     offset_1=$offset_2
 114                 fi
 115                 if [ $y_2 -ge $max_y  ]; then
 116                     offset_2=$offset_1
 117                 fi
 118                 for (( x=0; x<$max_x; x++ )); do
 119                     off_1=$(($offset_1+$x))
 120                     off_2=$(($offset_2+$x))
 121                     new_map+=($((${map[$off_1]} | ${map[$off_2]})))
 122                 done
 123             done
 124             map=("${new_map[@]}")
 125             max_y=$new_max_y
 126             ;;
 127     esac
 128 }
 129
 130 get_points_count() {
 131     local count=0
 132     for point in "${map[@]}"; do
 133         ((count+=$point))
 134     done
 135
 136     echo $count
 137 }
 138
 139 #display_map
 140
 141 # do first fold
 142 fold "${folds[0]}"
 143 echo
 144 #display_map
 145 echo
 146 echo "There are $(get_points_count) dots visible after first fold"
 147 for (( f=1; f<${#folds[@]}; f++ )); do
 148     echo "Doing fold $((f+1)) of ${#folds[@]}"
 149     fold "${folds[$f]}"
 150 done
 151 echo
 152 echo "After all folds:"
 153 display_map