2019 day 3 + add br.h for some useful stuff (min, max... macros)

2019/day03/README.org

@@ -55,12 +55,61 @@ 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=
+- =R75,D30,R83,U83,L12,D49,R71,U7,L72U62,R66,U55,R34,D71,R55,D58,R83= =
+  distance =159=
+- =R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51U98,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]].
+Your puzzle answer was =860=.
+
+** --- Part Two ---
+It turns out that this circuit is very timing-sensitive; you actually
+need to /minimize the signal delay/.
+
+To do this, calculate the /number of steps/ each wire takes to reach
+each intersection; choose the intersection where the /sum of both wires'
+steps/ is lowest. If a wire visits a position on the grid multiple
+times, use the steps value from the /first/ time it visits that position
+when calculating the total value of a specific intersection.
+
+The number of steps a wire takes is the total number of grid squares the
+wire has entered to get to that location, including the intersection
+being considered. Again consider the example from above:
+
+#+BEGIN_EXAMPLE
+  ...........
+  .+-----+...
+  .|.....|...
+  .|..+--X-+.
+  .|..|..|.|.
+  .|.-X--+.|.
+  .|..|....|.
+  .|.......|.
+  .o-------+.
+  ...........
+#+END_EXAMPLE
+
+In the above example, the intersection closest to the central port is
+reached after =8+5+5+2 = 20= steps by the first wire and =7+6+4+3 = 20=
+steps by the second wire for a total of =20+20 = 40= steps.
+
+However, the top-right intersection is better: the first wire takes only
+=8+5+2 = 15= and the second wire takes only =7+6+2 = 15=, a total of
+=15+15 = 30= steps.
+
+Here are the best steps for the extra examples from above:
+
+- =R75,D30,R83,U83,L12,D49,R71,U7,L72U62,R66,U55,R34,D71,R55,D58,R83= =
+  =610= steps
+- =R98,U47,R26,D63,R33,U87,L62,D20,R33,U53,R51U98,R91,D20,R16,D67,R40,U7,R15,U6,R7=
+  = =410= steps
+
+/What is the fewest combined steps the wires must take to reach an
+intersection?/
+
+Your puzzle answer was =9238=.
+
+Both parts of this puzzle are complete! They provide two gold stars: **