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+=("$dot")
  95                     new_offset=$((($y * $new_max_x) + $x))
  96                     new_map[$new_offset]=$((${map[$offset_1]} | ${map[$offset_2]}))
  97                 done
  98             done
  99             map=("${new_map[@]}")
 100             max_x=$new_max_x
 101             ;;
 102         y)
 103             local new_max_y=$(($max_y - $point - 1))
 104             if [ $point -gt $new_max_y ]; then
 105                 new_max_y=$point
 106             fi
 107             local adj=$((max_y % 2))
 108             for (( y=0; y<$new_max_y; y++ )); do
 109                 # do the y offsets here
 110                 y_1=$(($point - $new_max_y + $y))
 111                 y_2=$(($max_y - ($new_max_y - $point) - $y - $adj))
 112                 offset_1=$(($y_1 * $max_x))
 113                 offset_2=$(($y_2 * $max_x))
 114                 if [ $y_1 -lt 0 ]; then
 115                     offset_1=$offset_2
 116                 fi
 117                 if [ $y_2 -ge $max_y  ]; then
 118                     offset_2=$offset_1
 119                 fi
 120                 for (( x=0; x<$max_x; x++ )); do
 121                     off_1=$(($offset_1+$x))
 122                     off_2=$(($offset_2+$x))
 123                     new_map+=("$dot")
 124                     new_offset=$((($y * $max_x) + $x))
 125                     new_map[$new_offset]=$((${map[$off_1]} | ${map[$off_2]}))
 126                 done
 127             done
 128             map=("${new_map[@]}")
 129             max_y=$new_max_y
 130             ;;
 131     esac
 132 }
 133
 134 get_points_count() {
 135     local count=0
 136     for point in "${map[@]}"; do
 137         ((count+=$point))
 138     done
 139
 140     echo $count
 141 }
 142
 143 #display_map
 144
 145 # do first fold
 146 fold "${folds[0]}"
 147 echo
 148 #display_map
 149 echo
 150 echo "There are $(get_points_count) dots visible after first fold"
 151 for (( f=1; f<${#folds[@]}; f++ )); do
 152     echo "Doing fold $((f+1)) of ${#folds[@]}"
 153     fold "${folds[$f]}"
 154 done
 155 echo
 156 echo "After all folds:"
 157 display_map