2019 day3 init

2019/day03/README.org

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+** --- Day 3: Crossed Wires ---
+The gravity assist was successful, and you're well on your way to the
+Venus refuelling station. During the rush back on Earth, the fuel
+management system wasn't completely installed, so that's next on the
+priority list.
+
+Opening the front panel reveals a jumble of wires. Specifically, /two
+wires/ are connected to a central port and extend outward on a grid. You
+trace the path each wire takes as it leaves the central port, one wire
+per line of text (your puzzle input).
+
+The wires twist and turn, but the two wires occasionally cross paths. To
+fix the circuit, you need to /find the intersection point closest to the
+central port/. Because the wires are on a grid, use the
+[[https://en.wikipedia.org/wiki/Taxicab_geometry][Manhattan distance]]
+for this measurement. While the wires do technically cross right at the
+central port where they both start, this point does not count, nor does
+a wire count as crossing with itself.
+
+For example, if the first wire's path is =R8,U5,L5,D3=, then starting
+from the central port (=o=), it goes right =8=, up =5=, left =5=, and
+finally down =3=:
+
+#+BEGIN_EXAMPLE
+  ...........
+  ...........
+  ...........
+  ....+----+.
+  ....|....|.
+  ....|....|.
+  ....|....|.
+  .........|.
+  .o-------+.
+  ...........
+#+END_EXAMPLE
+
+Then, if the second wire's path is =U7,R6,D4,L4=, it goes up =7=, right
+=6=, down =4=, and left =4=:
+
+#+BEGIN_EXAMPLE
+  ...........
+  .+-----+...
+  .|.....|...
+  .|..+--X-+.
+  .|..|..|.|.
+  .|.-X--+.|.
+  .|..|....|.
+  .|.......|.
+  .o-------+.
+  ...........
+#+END_EXAMPLE
+
+These wires cross at two locations (marked =X=), but the lower-left one
+is closer to the central port: its distance is =3 + 3 = 6=.
+
+Here are a few more examples:
+
+- =R75,D30,R83,U83,L12,D49,R71,U7,L72=
+  =U62,R66,U55,R34,D71,R55,D58,R83= =distance =159=
+- =R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51=
+  =U98,R91,D20,R16,D67,R40,U7,R15,U6,R7=   =distance =135=
+
+/What is the Manhattan distance/ from the central port to the closest
+intersection?
+
+To begin, [[file:3/input][get your puzzle input]].