Advent of Code – Day 3

Continuing with the language-independent code challenge on Advent of Code – Day 3, I’m tasked with figuring out how well a drunken elf can guide Santa to houses.  Since his instructions had Santa stumbling into the same house multiple times they then added in a robot to help Santa using the same instruction set, which went on to prove automation can be harmful if not done properly.

Wow, I bet you never thought you’d read that paragraph…

The elf gave Santa instructions on how to get around a grid of houses using ^, v, <, and > to point the way.  When that failed, they tried again with a robot assistant using the same instructions with Santa taking the odd numbered instructions and his automated assistant taking the even numbered instructions.

My code did not have to change much to partially automate Santa’s job, which is actually kinda disturbing.  However, since it didn’t work out so well I went back and added a parameter for them to easily roll back the change.  Now it’s easier to go back to happy and jolly instead of cold and…terminator.

SET NOCOUNT ON

IF OBJECT_ID('TempDB..#visited') IS NOT NULL BEGIN
	DROP TABLE #visited
END

DECLARE @input varchar(max) = '>^^v^<>v<<<v<v^>>v^^^<v<>^^><^<<^vv>>>^<<^>><vv<<v^<^^><>>><>v<><>^^<^^^<><>>vv>vv>v<<^>v<>^>v<v^<>v>><>^v<<<<v^vv^><v>v^>>>vv>v^^^<^^<>>v<^^v<>^<vv^^<^><<>^>><^<>>><><vv><>v<<<><><>v><<>^^^^v>>^>^<v<<vv^^<v<^<^>^^v^^^^^v<><^v><<><^v^>v<<>^<>^^v^<>v<v^>v>^^<vv^v><^<>^v<><^><v^><><><<<<>^vv^>^vvvvv><><^<vv^v^v>v<<^<^^v^<>^<vv><v<v^v<<v<<^^>>^^^v^>v<><^vv<<^<>v<v><><v^^><v<>^^>^^>v^>^<<<<v><v<<>v><^v>^>><v^^<^>v<vvvv<>>>>>^v^^>v<v<^<vv>^>^vv^>vv^^v<<^<^^<>v>vv^v>><>>>v^>^>^^v<>^<v<<>^vv>v^<<v>v<<><v>^vvv<v<vvv^v<vv<v^^^>v><<^<>><v^^>^v^>>^v<^<><v<>>v^<>>v<>>v^^^><^>>vvvv>^v<^><<>>^<>^>vv><v<<>>^^>v^^^><^<<^^v>v<^<<>v>^^vvv^v^>v^<>^^<>v^v>v>v<v^>vv>^^v<>v>>^<>><>v>v^<<vvvv<vvv><v^<^>^v<>>^><v>><>^<v>v<v>vv^>>vvv<>v>v<v^>>^>>v<<>^<>^<>>>^v<<<^<^v>vv^>><<><v^>^v^^^v<>^^vv><>><>>^>v^<v<>v<>>^<<^v>^^^<>^v^><>v<<v>vv^>vv<<>>><<^v^<>v<vv>>>^^<>^><<^>vv>>^<<v^^vv<>>><v>v><^<v<<>>>^^<>>^<^v><>vv^^^v>vvv>^><<>^^>^<<v^<v<^v<<>vvv<^<<>^>^v<vv<^>vvv>v>vv^<v^><>>^vv<^^^vv><^vv<v^<><v^vvv><<^>^^><v<<vv^>v<vv<v>^<>^v<<>v<v^v^>^>^>v<<^vvv<<<v>^^>^<<<<>vv>>^<>^>>>v<v>^^<v^<v<>>>vv>^^v<<>>>^^v><<<v<v<^v<>^^><v<^v<<v^><><^<><v<^^v>>><v^^v<<v^><^<><<v^>><^<>v>v^<><^<v>^v^>^>^vv^>^^<<vv^>vv<^vvv<>>^^<^>v^>^>^<v^><v<v>>>v<<<><^v<<><^<vv^v^^^>v<^^<v^vvv<v<><v<vv<^vv<>vv<v^<>>vvvvv<<>^v^v>vv>>>vvv^^<^<^<><>v<v>><^v><^<<<>><<<v>^>v<>^>^v>>^<>v^<^>><<>^<v>^>^^^>^^<v>>>><>^v^v><<<<vv^<vv<>vv>v<>v^<v^>v><>>>v^<><^vvv>vv^<^<<^<^^v>^>>>v<^<^v^^<^<^>>><v>vv>^<<><>^>>v>^<<>><^<>v<>vv^^>^>vvv^v<<^<^^<vv<>^vvv<^^v^vv^>>v<^>^^<v^<>v<^<^vv>v<<vv>vv>^>vvv>>>^^>v<>^v>v^<^>>v>^^v>>>>v^<v>v<^>v<v<<>>^v<^^<v><^<>>^<<vv^>>v<<v>^v<>><^>vv<v<^>>^^<vvvvvvvvv>>>v<v<>v^<>>^vv<v^^v<<^vvv^<<^><>vv<><<>>v>vv^><>>^^v^>>v^v^><<<>>^^<^v<<^<>>>>^<^>v^><<^>v<^v<^>>^^<<<<><^<^v^v<>>^v<^<<vv^<><^^vv><v^v^v>^>>^>^vv^>^v<v^v<<vvv^><>>^v^^><>v>vv><^>>vv<vvv<<<<^<>vvv^v<v>^<v<^>^<^<v<><>v^^^^<<vv<^^vv<v>><<v^><>>><v^>^v><^>^><vv^<><^<v>><<^vv<>>v^<<v<>v><v<><><vv>^>>v^<^<v>^><>>><^><v^v<>>>^^<^>v<v>vvv<>^<<><v^^>^>>v<^v>^>v>>>vv>v>>v^^^<^<vvv^<>^>^<v^<v^v>v>^>vv>vvv<>v<^>v>^^>>^<vv^^v>v^^^^^v^vv><^<><>^>vv<^>>^vvvv^^^>^<vv>^v<<^><^^>^<>^^>^<<v<^>>>^><<^^>v^v>>^>vvvv>^^v><v>>vv><<<vv<^>v>^^^<v>v^vvv<^><<^>^<>^><<<<<v^<<vv^v>^<>v<v>^>^>><>v^v<^vv^^>vv<<v^v>vv^vvv<<<<>^v<v^^v^v>v<<v>^^<>^vv^^>^>^v^vv^>>v^vv^^<vv><<v^v^^v><vv<^vvv<vv^^<<v>v^v^^^^v<^<^>v>^>v>^vv^v^^<v<^vvvv<<<>^<^^^<^^<>^<><vv<^^<<^>>><v^vvvv>^<>>^^>v^^v^<<v^^^<<<><^<v^v^^v<v^<>v><<v<>^v>v<^><^>vv^^<vvv<^v>>v>^<><v^><^^^<v^>>vv<<<<<^<>^v^v>^vv^<>v>v<^>vv<<^vv>vv<v<><>>v>><v<^<^^>><<v^v<<^><v<^<vv<v<<vv^>^<<><^^>^<^>>^<vv>><v<<vvv<^^v^>^^<^v>^v<v<>v><v^v^<<^<><<v<<^v>v<<>>^>v>>v>>v<^<<^<^>>>v>^^^v><^>^^>>v<<>^v><v>vvv^vv<<<>vvv<<>^>>>v<v<v^<^<^>^<^>v^^v<^^<v<>v<>>^^>^v^>v<<<<^<>v^><<<v>>>><<v^<^vv>v>><>>^<<<^<^^>v<>>v<>vv<<^<<><<^>v^^^vv^>vvvv>>v>v^><<v<>vv^<<><<vvv>^>>>^<<<^<^<<v>^>v<>>v>>vv^^><<<<^^^v>><<^><v><v^^><v<<v^^v^^v>>v<><><<>^><v><^<vv>><^v<>v<vvv<>^>><v>>v<^><<v>^<>^v><^><^^<v>^><^^v^<<><>>^>v^<^v^vv<><^>vv^>v^vvv^<>>^><^<^<>^<<v^v<^v><>^v<v>>^>>^v^vv>><vv><v^^<<^v^<>^v<<>^><^>><v>>v<<<v^^vv<>^^v>>><><><<v^<<<v^<^^><v^>v^^vv<v^<>>vv^<^v<>^v>>v^v>v<^^vv><>^v<<>v^<>v^>>v>vvv<^><><^^>^vv^>>v^>^<^^<><>><<>^^^><^v^v><<<><<^v^vv>v>><^>>><v^>v<v><><v^v<>v^^>>v<<>v>v<v<v<^^<><>v^^<>>v<^v<v>v<><v<v>^<<>v>vv^^<>>^^^<>^^>^v>v>>>^v^v><v^^<><v>^^v^v<^<^^><<v<^<^<>^<>><<>^>>^>^^><v><>v<><>><<<>>>>vv>>>^>>^v<^>v^^^v<<vv>><<<^<<<>>>>>^>vv<^v^<>^<v^>^v><v>vvv<>>>^v^^^v<<<<>>^^<vv<^<^^>^<>v<^<<<>><>>v<^<>^<vvv<^<>><><<v>^^^>^^<<v<v^>^^v^>><<^vv><v>^v>>^<v>v>^^>^v>^vvv<>v^v^^<><vv>vv^>>><>v<^><v<v^<><<<>^v>^v<<<^>^>^>v^v<<><vvv<<v^^<><v>^>>><vv>><v>>v^<vv>>vv<<^v^v<<><^v<vv>>>vv<>>>>^vv>v^<>vv>v^v<v^><v<^^^^^>vv<><<vvv^<v><^<vv><^^^vv^<>^^^^<^><^<>v^<v^v<<^v<<^^<>>^<v^^>>>vv<vvv<>v<<>><^vvv^<<^^<<>>>^<>>>v^^><>><<>><v^v>>>>>><>>><v^<<vvv^>v<>>v^<>vv<><^^^^v^<<^<v^vv><<^^>v<^vvv^v>>v>^>>v>^^><<v^<>v<>vv<^v^vv><v><<vv^v>>v^>>v<^^^>^><<v<>^><>v>>>vvv<v<vv<^>>^v<v>^<^^^^^v><>v><>v^v^v<v^vv^v>vvvv<>vv<<<vv<v<<>^<^>^^v^<<>^<v><^><v<v<><<>v^<<^<><vv>v<<^v>>^v<><v>^>>^^><>v^<^<vvv^>^>^<<<<>vv>^v^v<^^^<vv>><>^^<<v<^<^^>>>v^v<<^^^<v<v<^<>^v<v><v^vv^^v^^v^^<vv<>^<><vv^<^v^<<^><<vvv>^^<^^^<^v>^>^vv><<<^v<v>vv>v<>v^v<v^>v^>>>v^v<>^v<<>^vv>v>v>v^<^>v^^<^>^^^^vv>^^><^>vv^>>^^v>><<<<^><>v<>^<v<vv^>^^><<^><v>v^>^^<^>>><>><v^v<v^<v<vv^v^<<^<vvv>>><vv<^^>>^>^><<v^<>>v>v^v^^><<>vv^v>v^<v><^<>^^<^>v>^<><<<v>^<^<^>^>^>^^v^<<^^v^^<^<>><^>v>>^^<>^^^<<<<v^>^v<^vv>^<<<v<><<v<>vv>>>v><>>><>>v<<<vv><>^v>v<^>><^><><v<>^v^>^v>^v<<><<^<>>v>^><>^>><>><^<v^><v^^<><v><^^>^v^^<>v^<v^<^v<v^^^^^v^<<^>^^^<^v><>^^<<<><<<<<^^>v^vvvv>v<>>vv<^>^v^>v<^vv^v<<><<v>v^v>^^><><^<v^>v><vv><>>><<>^vv<>v>>v<^v>>>v<v>v>v>^vv<<>^^vv<v<^v^<v<v>vv<>^<^<vv<v^<^v^^><<>^>><^v>vv^^v<<^^><<>v^^<><><v^^<v^v>^>^>^>v<^<v>^v^^>v<>vvv<^v<v^v><<v^><<^^><^<<v^v^>v<>^>v><><v>^<v<v>^<^^^>^v<<><<><>vv>v^<>v^><v^v<v><><<v>v<vv><<v>>v>^<<<>vv>>vvv>^^vv^v^^<^^<>v^^<>v>>^^>^>^>v>><^>><>>^<<>><^>v<<<<<<<^v^v<v^<v^^>^<><<v<^>v^>v^vv<<^^vv^>>>>^<>v<^v<>v<vv<^>>v^vv>vv><vv<<^>v>><vv>>>vv^<<<<vv^>v<<<<^^>^^v^><<^<v^>v^>^^<v<>vvv^>^<>vvv<v<^^>v^<<v>><>v<v<>^^<vvv>^>vv><><<<^^vv<v^<v<>v<>><<v><^vv^>^<^>^^^<<<v>vv^<^<<>^>^<vv>v><v<<^><^>^^<vv^v^^>>>>vv^><^^vv><>^<v^v>v<vv>v><<<v>v<v>^><v^^><v>v<^v^>>^^<v^>^^>vv>>vv^><^vv^vv<<^>vv>^v<v><vv><v<vvvvv>^^v^v><v>>>^vv<>v>^^^^<^>><>^v^^^>v<^^<<^^v<vv<>vvv<^>><><^>>^><^<>v<v<<><<v><v^v<>><^>v><<v^<v>v<^<vv^v^v^>vvv^^>v>^<vv^>v^v^<>v>^>>vv>><^^<v<<>^vv<><><<^v<v>v<<vv><>><^v<v>>v^>vvv^v^<<^><v<>^vv^>v^<v<^>>v<v><v><v>>^<<<v^<><<>v>^>^^<v<>>^<>^>^><<<^<<^<<^>^v>>><vvv>><<<<v>>>>>>>^<^v<^>v<>vv<><>v>>^>>^>vv^^><<^<v<v>>^^<<^>v<^>>vv>^<>v><^>v<vv>>>>>>^v<^<<<v^><vv<<>>vv<<><v<><<<v<^<v<>>v<^^^^v^^<^^^<^<vv><<^>><>v<<>v<v<>>>><>v^vv>^>^>>vv^v<v<<><^v>vv^><v<<>v^v<^>vv<<^^v><^>>^^vv<^<>>v^^>><v>^v>>>^>>v>v<>v<^vv><>^<<^>vv>>><><>v^><>v^>v>v><^v<><v<v>^v<<^vv^><^^>><^^^<<<^>v>^v>>><^>><^>>>^^^<^>vv<><<<v^>^<^^>>^^^v^v^v>v<v>>>><^>>>v>^vv<<^^^<^^vv>v<<><v<<^^>v>><<v^^><^>^<^>^v^>v><^<^vv>v>><>^<<vv<<v>v<vv<v>^>^>><^^<v>^v^v<><<>vvv<^<v>^><>^>vvv>>>^><<>><v^^<^<<^v>>^v<v<vv>vv^v^>v<<vvv<^^v^v>^<^>>^>v<^>^v<<><<<^>^<^^^>vv<^^^^vv<v<^^v<<<<v<^v^<><v<<^><<>vv>>><^<^<>>>^>^>>^<<<<<^^v>^>^<>vvv^^<^><^>^^v>^vv^><v^<^<<v^<vvv<<^v<><^><^>>>v>^v>^>^v<vv^v>><v><^><v^^>v^>^<><<><>v<v^>vvv^>^>>v<>^><^>^><vvv>^^v^v>v<>^v^><^>>v>v^><<<^>>^<>^<>>v><>>v^>^>^^<>>v^>^<vvvv<^vvvv^>>vv^<v^v>^vv<>v<>^<v<v>v>^^><^>vv^<^v^<<^<^<><vv<^v<^v><>>>^v^<<^><^>vv<v>v<^>vv^>v<<<>^<><v<^^^>v><^^<>^<^<v^vv^<<^>><<v^v<^vvv<<<>>vvvv^v^^^>v<>>><<>vvv<<^^^>v>v>>v<<v<v^v^>^^v>^><^<><<v^<v<v^^^><>v^^^<v>vv<>^>^^vv>^<<^v<^v><v>>>^>>><^<<>^v>>^>vv<<<v<>^<v><v^<^<>v>v^^v^>><<^v<<<<>v>v>v^^<^><>^^<<<v>vv<>>>^>>v<><v^>^<><vv>v>v^v<v^<^>>^>><<^^<^^v<vv<>><<<v<^<<^^^>vvv^<vvv<^>vv><>><<<^<v^v^^<<^vvv^^<^<><<>^<^<>>vvv<>^<>v^v<><>>v^v><<>>>vvv>v<>^>>^><^>vv<<>>v<<^><>v>>^^<v>^>^<<>><^<<vv<^<vv^vv><>>>><^<v>^>vv<v><>^<>vvvvv^vv<<v<>>>^<<><>^^vvv>>>vv<<^^><^v^^v<>^^>^><^>v^^^^v<^<<vv<vv<>vv^^>v^vv>v><>>vv>^<^<v^v^>>v^v^^v>^>vv^>v<vvvv<^v<^v>^v>^^v<<^>^^<<>^><^v>>>vv^>^^>vvvv>>v<^<v>^>>>v^<><^<^^<v>vv^^><v>v^<>^^^>>><^^v>v>^<<>^<v^>vvv^>^^^><v<^>>v<v>>^v><<><<>v<^<<>^><>^>vv>^<v>^^v<<^v^vvv^^>^vv^<^>^>^^v>v^>^<<><<^>v>>vv^vv><v>>^<<^<v^^<^<v^^vv^><^^<^^><v^^>v^^^<^<>^<>>^v<^vvv^^v^<><^>>>>>v><><<<>vv<^v>><<>vvv<><<vv<<<^>v^^>>^>^v>><><^^v<>><>>v^>^<vv><<<>><><<v>^^<>>v<><^<vv>vv<^v>^<<<<v<^<<^^>>^<><^>><<>^>v>^^^v>>^<^^v><v^v>^><<><>>^>>^<<v<>^v<>^>^<v>>vv>^vvv<<v<<^>^>^<<^^<>^^^^vvv<>^vv<vvvvv^^>^^<^>>><>v^<><^<<^>v^^v<>>^vv<>v^^<>>v^vvvvv<<v^<v^^>>><vvvvv>><^>vv>v^v^<v<^>^^><^>^^^^v<><^v<<>v^>v>>vv<<>^<v^^>vvv>^^<v^<>vv^><>><v^^v<>^>>^>v><>>^^v>^>^>>>^>v<^v>v>^<^^^^^>>v<v<>>v<<^>^<v<<>^^>><<^><>v<>^^^vv<>^^>><<^^>v>vv>vv>v^>^v>v^^<>>><<v><v<<>>v><>vvv^^v>^^>^vvvv^>^<>^vvvv><v><v<>>><>^<^vv<>^v<^v<>^vvv<<>><vvv^>>^><<vv^<v^>^<v<<^^>^^<^^v^>v<>v^v><>><v^^>>^vvv><^vv>v^<^<^v>>v^^>^vvv^<v^^v^^>v<^<>>^<>>>^^<><^^vv<>^vv^<>>>>^^<<^^<>vv^^><>^^<v<<v>^<v^^>^v<><><>vvv>^v^>>vv<<^v<<>><v>^><^>>>^<^<^^>vv^<<^<>>^^><><<v>^^<v>>v<<vvvv>^v^vv>><^^<<^>>v>v<^^^<^><^^vv>^vv<^<vv<>v><^<><v><^^^>>^<><^<v>>>>v^<v>>>>>v<><^^>v<^<^>><v<>^>vv>^^v^v^<<v<><<<^v^><<^<><<<<v<^>><<<>v>>vv><vv<><<^<^<><vv>^^^^<>v<<<<v>vv<>vv^^^>><>vv^><>>^vv<<><^^vv<>v^>>^<<>^<v^<^>v<'

DECLARE @sx smallint = 0
	, @sy smallint = 0
	, @rx smallint = 0
	, @ry smallint = 0
	, @useRobot bit = 0
	, @x smallint = 0
	, @y smallint = 0
	, @i smallint = 0
	, @i_max smallint = 0
	, @char char(1)

SELECT @i_max = len(@input)

CREATE TABLE #visited
(
	x smallint
	, y smallint
	, PRIMARY KEY (x,y)
)

WHILE @i <= @i_max BEGIN
	SELECT @char = substring(@input, @i, 1)

	IF @i % 2 = 0 AND @useRobot = 1 BEGIN
		SELECT @x = @sx
			, @y = @sy
	END ELSE BEGIN
		SELECT @x = @rx 
			, @y = @ry
	END

	IF @char = '>' BEGIN
		SELECT @x = @x + 1
	END ELSE IF @char = '<' BEGIN
		SELECT @x = @x - 1
	END ELSE IF @char = '^' BEGIN
		SELECT @y = @y + 1
	END ELSE IF @char = 'V' BEGIN
		SELECT @y = @y - 1 
	END

	IF 0 = (SELECT COUNT(1) FROM #visited WHERE x = @x AND y = @y) BEGIN
		INSERT INTO #visited(x, y) SELECT @x, @y 
	END

	IF @i % 2 = 0 AND @useRobot = 1 BEGIN
		SELECT @sx = @x
			, @sy = @y
	END ELSE BEGIN
		SELECT @rx = @x 
			, @ry = @y
	END

	SELECT @i = @i + 1
END

SELECT COUNT(1)
FROM #visited 

I’m not the only one doing this with T-SQL.  Andy Warren also posted his very different, yet same results, version in separate posts for the two parts: Day 3 Part 1 and Day 3 Part 2.  His came out more complex, but more set-based.

My problem is that I develop T-SQL for the problem at hand with the expected size of the data.  Andy is looking ahead and developed a method that will probably scale much better than mine.  I’m hedging my bets and hoping the elf in charge of this either sobers up or gets fired.

Advertisements

2 thoughts on “Advent of Code – Day 3

  1. You give me too much credit for looking ahead! My rule is to try to find a set based approach if I can see one. If I can’t, I’ll code a loop to solve the problem and increase my understanding of the problem, sometimes that helps me see a set based way. In practice I don’t assume set based is faster. If my first solution works well enough, I stop there. If it seems slow, or unlikely to scale, then I’ll try again and compare the two (or three sometimes).

    Its interesting that you only tracked the distinct visits (and thus the pkey on x & y). I tracked all, then figured out from there. Steve took your approach when he used a dictionary. Not better/worse, just different.

    • Set based is almost always scales better, so it’s a good approach. In fact, I’m almost expecting someone to ask me for an example where set based doesn’t scale better, for which I do not have an example.

      With the primary key, I got lucky that part 2 was still unique values and not finding what kid was the luckiest. I have to admit, I never saw the robot twist coming.

Questions are some of the sincerest compliments

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s