As I continue through the Advent of Code, albeit slowly, I’m solving each puzzle 3 days. I worked through 6 of them in Python before moving on to other languages, and this is my chance to catch up with both PowerShell and T-SQL. I likely won’t post all solutions, but I was having fun rewriting code, so here are the ways I looked at things.

Note: You should try this on your own. I logged into the AventofCode with GitHub and things worked great for me.

Go on, give it a try.

I’ll wait.

Solutions coming.

Python

I started here, using iterations, which are very powerful in Python. In this case, I took advantage of the multiple variable assignment in Python to enumerate the array and get each value and index. I think use a comparison to determine if I add or subtract one. Finally, an IF returns the current index if I hit –1. I should probably have a break in there for efficiency as well.

def calculate_negative(directions):
    start = 0
    for i, c in enumerate(directions):
        if c == '(':
            start += 1
        else:
            start -= 1
        if start == -1:
            print(i)

PowerShell

This was a bit trickier for me. I wasn’t sure how to work with a string and pull out values. I did some searching and ran across the .ToCharArray function. That doesn’t feel like the best way to do this, but I decided to use it.

The rest of the function is similar and gave me the correct answer, so there you go.

$count = 0
$floor = 0
foreach ($c in $input.ToCharArray())
  { 
   if ($c -eq '(') {$floor += 1} 
   elseif ($c -eq ')') {$floor -= 1 }
   $count += 1
   if ($floor -eq -1)
     {
     $count
     break
     }
  }

T-SQL

A more complex situation here, given that we need to work through a string, calculating a running total. I broke the input up using a tally table and a splitter with substring. This was fairly easy, and not complex as I was just getting individual charaters.

Then it was a simple running total of the CTE to get me the totals at each point in time. This worked well, but I needed the first –1 total.

Finally, I used the outer query to get the min value out of the code and use that, which gave me the lowest value where the –1 occurred.

WITH tally (n)
AS
( SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL))
   FROM (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) a(n)        -- 10
   CROSS JOIN (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) b(n)  -- x 10 = 100
   CROSS JOIN (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) c(n)  -- x 10 = 1000
   CROSS JOIN (VALUES (0), (1), (2), (3), (4), (5), (6), (7), (8), (9)) d(n)  -- x 10 = 10000
)
, direction (n, d)
AS
(
SELECT tally.n
   , d = CASE WHEN SUBSTRING(@input, n, 1) = '(' THEN 1 ELSE -1 end
 FROM tally
), currfloor 
as
(SELECT 
   d.n
   , 'currentfloor' = SUM(d.d) OVER (ORDER BY d.n ROWS UNBOUNDED PRECEDING)
FROM direction d
)
SELECT MIN(currfloor.n)
 FROM currfloor
WHERE currentfloor = -1

Filed under: Blog Tagged: AdventofCode, powershell, python, syndicated, T-SQL