AOC2019day3part2

3-2.sh

#!/bin/bash

set -eu
set -o pipefail

xorigin=1000
yorigin=1000

wires=()

while read -r wire; do
  wires+=("$wire")
done

wirepositions() {
  wire=$1

  IFS=, read -r -a directions <<<"$wire"

  x=$xorigin
  y=$yorigin
  length=0

  move() {
    distance=$1
    deltax=$2
    deltay=$3
    while [ $((distance--)) -gt 0 ]; do
      x=$((x+deltax))
      y=$((y+deltay))
      length=$((length+1))
      echo "$length:$x,$y"
    done
  }

  for instruction in "${directions[@]}"; do
    case $instruction in
      U*) move "${instruction#U}"  0  1 ;;
      D*) move "${instruction#D}"  0 -1 ;;
      L*) move "${instruction#L}" -1  0 ;;
      R*) move "${instruction#R}"  1  0 ;;
    esac
  done
}

join -j 2 -t : \
  <(wirepositions "${wires[0]}" | sort -t : -k 2) \
  <(wirepositions "${wires[1]}" | sort -t : -k 2) | \
  sed -e 's/.*:\(.*\):\(.*\)/\1 + \2/' \
  | bc | sort -n |head -n 1