day3/wires_2.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     local -n w1cost=$4
  28     wire_number=$5
  29     cur_vert=0
  30     cur_horz=0
  31     moved=0
  32     last_replace_char="-"
  33     cost=0
  34
  35     for operation in "${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${operator}1))
  57                     cost=$((cost+1))
  58                     if [ $wire_number -eq 1 ]; then
  59                         if ! [ ${w1cost[$cur_horz,$cur_vert]+a} ]; then
  60                             w1cost[$cur_horz,$cur_vert]=$cost
  61                         fi
  62                     fi
  63                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  64                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  65                             cross_wires[$cur_horz,$cur_vert]=$((${w1cost[$cur_horz,$cur_vert]}+$cost))
  66                             b[$cur_horz,$cur_vert]=3
  67                         fi
  68                         continue
  69                     fi
  70                     b[$cur_horz,$cur_vert]=$wire_number
  71                 done
  72                 ;;
  73             L|R)
  74                 for (( moved=1; moved <= $amount; moved++ )); do
  75                     cur_horz=$((cur_horz${operator}1))
  76                     cost=$((cost+1))
  77                     if [ $wire_number -eq 1 ]; then
  78                         if ! [ ${w1cost[$cur_horz,$cur_vert]+a} ]; then
  79                             w1cost[$cur_horz,$cur_vert]=$cost
  80                         fi
  81                     fi
  82                     if [ ${b[$cur_horz,$cur_vert]+a} ] && [ $wire_number -eq 2 ]; then
  83                         if [ ${b[$cur_horz,$cur_vert]} -eq 1 ]; then
  84                             cross_wires[$cur_horz,$cur_vert]=$((${w1cost[$cur_horz,$cur_vert]}+$cost))
  85                             b[$cur_horz,$cur_vert]=3
  86                         fi
  87                         continue
  88                     fi
  89                     b[$cur_horz,$cur_vert]=$wire_number
  90                 done
  91                 ;;
  92         esac
  93     done
  94 }
  95
  96 declare -A board
  97 declare -A cross_wires
  98 declare -A wire_1_cost
  99 echo "Tracing first wire"
 100 trace_wire wire_1 board cross_wires wire_1_cost 1
 101 echo "Tracing second wire"
 102 trace_wire wire_2 board cross_wires wire_1_cost 2
 103
 104 echo "Wires cross at:"
 105 min_cost=-1
 106 for cross in "${!cross_wires[@]}"; do
 107     echo "  $cross ${cross_wires[$cross]}"
 108     cost=${cross_wires[$cross]}
 109     if [ $min_cost -lt 0 ] || [ $min_cost -gt $cost ]; then
 110         min_cost=$cost
 111     fi
 112 done
 113
 114 echo Min cost: $min_cost