01.md

Day 01

Part 1

Find the floor number where Santa ends up on. Starting on the ground floor (floor 0).
( = go up one floor.
) = go down one floor.

Simple arithmetics:

const input = '((((()(()'

const up = input.match(/\(/g).length
const down = input.match(/\)/g).length
const result = up - down

console.log(result)

Try it out on flems.io

Part 2

Find the nth parenthesis (starts from 1) which takes Santa to the basement (floor -1).

let floor = 0
const result =
  1 +
  [...input].findIndex((parenthesis) => {
    floor += parenthesis === '(' ? 1 : -1
    return floor === -1
  })

console.log(result)

flems

Because the first parenthesis is at position 1 (as per the puzzle instructions), the 1 + before [...input].findIndex() is required. Initializing floor to 1 and removing the 1 + would also provide the correct result, but it would be confusing.

I don't like that I have to use a mutable variable (floor), but I can't think of a cleaner solution. I could use reduce(), but I couldn't make it pretty. Plus it would always loop through the whole input string; findIndex() stops when the result has been found.

What did I learn?

Nothing as this was a trivial puzzle.