day03/wires.sh

   1 #!/bin/bash
   2
   3 set -u
   4 set -e
   5
   6 # these wires should give 6
   7 #wire_1=(R8 U5 L5 D3)
   8 #wire_2=(U7 R6 D4 L4)
   9
  10 # these wires should get 159
  11 #wire_1=(R75 D30 R83 U83 L12 D49 R71 U7 L72)
  12 #wire_2=(U62 R66 U55 R34 D71 R55 D58 R83)
  13
  14 # these wires should get 135
  15 #wire_1=(R98 U47 R26 D63 R33 U87 L62 D20 R33 U53 R51)
  16 #wire_2=(U98 R91 D20 R16 D67 R40 U7 R15 U6 R7)
  17
  18 filename=${1:-input.txt}
  19
  20 # read in data from file instead
  21 exec 3<"$filename"
  22 IFS="," read -u 3 -a wire_1
  23 IFS="," read -u 3 -a wire_2
  24
  25 trace_wire() {
  26     local -n w=$1
  27     local -n b=$2
  28     local -n c=$3
  29     wire_number=$4
  30     cur_vert=0
  31     cur_horz=0
  32     moved=0
  33     last_replace_char="-"
  34
  35     for operation in "${w[@]}"; do
  36         direction=${operation:0:1}
  37         amount=${operation:1}
  38         case $direction in
  39             U)
  40                 operator=+
  41                 ;;
  42             D)
  43                 operator=-
  44                 ;;
  45             L)
  46                 operator=-
  47                 ;;
  48             R)
  49                 operator=+
  50                 ;;
  51         esac
  52
  53         case $direction in
  54             U|D)
  55                 for (( moved=1; moved <= $amount; moved++ )); do
  56                     cur_vert=$((cur_vert${operator}1))
  57                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  58                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  59                             c+=($cur_horz,$cur_vert)
  60                             b[$cur_horz,$cur_vert]=3
  61                         fi
  62                         continue
  63                     fi
  64                     b[$cur_horz,$cur_vert]=$wire_number
  65                 done
  66                 ;;
  67             L|R)
  68                 for (( moved=1; moved <= $amount; moved++ )); do
  69                     cur_horz=$((cur_horz${operator}1))
  70                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  71                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  72                             c+=($cur_horz,$cur_vert)
  73                             b[$cur_horz,$cur_vert]=3
  74                         fi
  75                         continue
  76                     fi
  77                     b[$cur_horz,$cur_vert]=$wire_number
  78                 done
  79                 ;;
  80         esac
  81     done
  82 }
  83
  84 declare -A board
  85 declare -a cross_wires
  86 echo "Tracing first wire"
  87 trace_wire wire_1 board cross_wires 1
  88 echo "Tracing second wire"
  89 trace_wire wire_2 board cross_wires 2
  90
  91 echo "Wires cross at:"
  92 min_distance=-1
  93 for cross in "${cross_wires[@]}"; do
  94     echo "  $cross"
  95     horz=${cross%,*}
  96     horz=${horz//-/}
  97     vert=${cross#*,}
  98     vert=${vert//-/}
  99     distance=$((horz+$vert))
 100     if [ $min_distance -lt 0 ] || [ $min_distance -gt $distance ]; then
 101         min_distance=$distance
 102     fi
 103 done
 104
 105 echo Min distance: $min_distance