day1

day 1

Day 1 - Advent of Code 2024

example input

3   4
4   3
2   5
1   3
3   9
3   3

Part 1

1. get left and right lists from the input
2. sort each list into numerical order
3. find the sum of the differences between each pair of numbers

first, do the fun bit and solve the problem

sort each list into numerical order

if the input is

[3 4 2 1 3 3]
[4 3 5 3 9 3]

then we want to sort each array into order ⍆:⍆ sort flip sort

which gives

[3 3 3 4 5 9]
[1 2 3 3 3 4]

(no need to flip back as we only care about differences)

find sum of the differences between each pair of numbers

then just subtract one array from the other, absolute value everything to get distances, and add up /+⌵- reduce add abs subtract

solution (without input)

📩 ← /+⌵-⍆:⍆

then, wrangle the input

💾 (reads the file in)

• &fras file - read all to string

📋 (get the data out of the file)

• ⊜□¬ ⊸⌕ "\n" partition box not by find "\n"
• splits input into separate lines
• puts each line into a box
• result is {"3   4" "4   3" "2   5" "1   3" "3   9" "3   3"}

🗒️ (parse one row of the input)

• given a single row of that array (eg ⊢ first) I can split it by spaces and parse it, use ⋕ ⊜□¬ ⊸⌕ " " °□ to turn it from {"3   4"} into [3 4]

≡🗒️📋💾

• ≡ rows does the parsing on every line of the input
• result is

╭─     
╷ 3 4  
  4 3  
  2 5  
  1 3  
  3 9  
  3 3  
	  ╯

reformat this into what we wanted

• °⊟⍉ uncouple transpose this gives the input in the form I wanted to start with, hurray!

[4 3 5 3 9 3]
[3 4 2 1 3 3]

⭐️ Solution

Using real input 📩°⊟⍉≡🗒️📋💾 gave the correct solution.

Afternotes

A more succinct way to parse the input

⊜(⊜⋕⊸≠@ )⊸≠@\n (from Kaikalii on the uiua discord)