day3/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 # read in data from file instead
  19 exec 3<input.txt
  20 IFS="," read -u 3 -a wire_1
  21 IFS="," read -u 3 -a wire_2
  22
  23 trace_wire() {
  24     local -n w=$1
  25     local -n b=$2
  26     local -n c=$3
  27     wire_number=$4
  28     cur_vert=0
  29     cur_horz=0
  30     moved=0
  31     last_replace_char="-"
  32
  33     for operation in "${w[@]}"; do
  34         direction=${operation:0:1}
  35         amount=${operation:1}
  36         case $direction in
  37             U)
  38                 operator=+
  39                 ;;
  40             D)
  41                 operator=-
  42                 ;;
  43             L)
  44                 operator=-
  45                 ;;
  46             R)
  47                 operator=+
  48                 ;;
  49         esac
  50
  51         case $direction in
  52             U|D)
  53                 for (( moved=1; moved <= $amount; moved++ )); do
  54                     cur_vert=$((cur_vert${operator}1))
  55                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  56                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  57                             c+=($cur_horz,$cur_vert)
  58                             b[$cur_horz,$cur_vert]=3
  59                         fi
  60                         continue
  61                     fi
  62                     b[$cur_horz,$cur_vert]=$wire_number
  63                 done
  64                 ;;
  65             L|R)
  66                 for (( moved=1; moved <= $amount; moved++ )); do
  67                     cur_horz=$((cur_horz${operator}1))
  68                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  69                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  70                             c+=($cur_horz,$cur_vert)
  71                             b[$cur_horz,$cur_vert]=3
  72                         fi
  73                         continue
  74                     fi
  75                     b[$cur_horz,$cur_vert]=$wire_number
  76                 done
  77                 ;;
  78         esac
  79     done
  80 }
  81
  82 declare -A board
  83 declare -a cross_wires
  84 echo "Tracing first wire"
  85 trace_wire wire_1 board cross_wires 1
  86 echo "Tracing second wire"
  87 trace_wire wire_2 board cross_wires 2
  88
  89 echo "Wires cross at:"
  90 min_distance=-1
  91 for cross in "${cross_wires[@]}"; do
  92     echo "  $cross"
  93     horz=${cross%,*}
  94     horz=${horz//-/}
  95     vert=${cross#*,}
  96     vert=${vert//-/}
  97     distance=$((horz+$vert))
  98     if [ $min_distance -lt 0 ] || [ $min_distance -gt $distance ]; then
  99         min_distance=$distance
 100     fi
 101 done
 102
 103 echo Min distance: $min_distance