aoc2023

Commit: f7381f4c7d14c3cc7b55a9a4495cadcf74e4d312
Parent: 7044de2c535ad1e651dc934bfbb835e203202059
Author: Randy Palamar
Date:   Mon, 11 Dec 2023 07:01:21 -0700

day 6

Using Haskell's list comprehensions for this almost feels like
cheating; it made this task completely trivial.

There is probably a faster way of doing this, particularly for
part 2, but I like the simplicity of this solution.

(Solutions are out of order and I'm falling behind but oh well).

Diffstat:
A
day6/day6.hs
 | 
44
++++++++++++++++++++++++++++++++++++++++++++
A
day6/test
 | 
2
++

2 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/day6/day6.hs b/day6/day6.hs
@@ -0,0 +1,44 @@
+-- AOC 2023: Day 6 - Wait For It
+--
+-- Given a set of (time, distance) pairs, an acceleration of 1
+-- dist/time^2 (units don't matter), and the rule that while
+-- accelerating you are not moving find the number of different ways
+-- you can reach the distance (i.e. you accelerate for a some portion
+-- of the time and then travel at the achieved velocity for the
+-- remainder).
+--
+-- Example input:
+-- Time:      7  15   30
+-- Distance:  9  40  200
+-- Test Output: 288
+--
+-- Task 2: There is actually only one time and distance in the
+-- example input with some random space in between.
+-- Test Output: 71503
+--
+{-# LANGUAGE OverloadedStrings #-}
+
+import qualified Data.Text as T
+import qualified Data.Text.IO as TI
+import Text.Printf (printf)
+
+texttoint :: T.Text -> Int
+texttoint t = read (T.unpack t) :: Int
+
+numlist :: T.Text -> [Int]
+numlist = map texttoint . filter (/= "") . T.splitOn " " . T.strip
+
+winningwaits :: (Int, Int) -> Int
+winningwaits (t, d) = length $ [x | x <- [1 .. (t - 1)], x * (t - x) > d]
+
+main = do
+    contents <- TI.getContents
+    let (t, d) = T.breakOn "\n" contents
+    let times = T.dropWhile (/= ' ') t
+    let dists = T.dropWhile (/= ' ') d
+    let pairs = zip (numlist times) (numlist dists)
+    let pairs2 =
+            ( texttoint $ T.filter (/= ' ') times
+            , texttoint $ T.filter (/= ' ') dists)
+    printf "Task 1: %8d\n" (foldl (*) 1 $ map winningwaits pairs)
+    printf "Task 2: %8d\n" (winningwaits pairs2)
diff --git a/day6/test b/day6/test
@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200