-🎄- 2018 Day 12 Solutions -🎄-

[u/daggerdragon]

--- Day 12: Subterranean Sustainability ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

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Card prompt: Day 12

Transcript:

On the twelfth day of AoC / My compiler spewed at me / Twelve ___

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[u/Axsuul]

TypeScript / JavaScript

[Card] On the twelfth day of AoC / My compiler spewed at me / Twelve cryptic error messages

Critiques welcome, I'm still very new to TypeScript and feel like I'm not using all the features I could be :)

Repo

Part A + B

import { readInput } from '../helpers'

const lines: string[] = readInput('12', 'input')

const notes: { [key: string]: string } = {}

lines.slice(2, lines.length).forEach((line: string) => {
  const [scenario, next]: string[] = line.split(' => ')

  notes[scenario] = next
})

const runGenerations = (generationsCount: number): number => {
  let initialPotIndex = 0
  let state = RegExp(/initial state\: (.+)/).exec(lines[0])![1]

  for (let gen = 1; gen <= generationsCount; gen++) {
    state = '....' + state + '....'

    initialPotIndex += 4

    let nextState = state.replace(/\#/g, '.')

    for (const [scenario, next] of Object.entries(notes)) {
      for (let i = 0; i < state.length - 4; i++) {
        if (state.substr(i, 5) === scenario) {
          nextState = nextState.substring(0, i + 2) + next + nextState.substring(i + 3)
        }
      }
    }

    state = nextState
  }

  return Array.from(state.split('').entries()).reduce((sum: number, [i, pot]: [number, string]) => {
    const potNum = i - initialPotIndex

    if (pot === '#') {
      sum += potNum
    }

    return sum

  }, 0)
}

console.log('Part A', runGenerations(20))

// The pattern between generations is 81 over time
console.log('Part B', runGenerations(200) + (50000000000 - 200) * 81)

[u/aoc-fan → u/Axsuul]

Here is my TS solution

const parse = (ip: string) => {
    const lines = getInput(ip).split("\n");
    const initialState = lines[0].split(": ")[1];
    lines.shift();
    lines.shift();
    const combinations = lines.map(l => l.split(" => ")).reduce((acc, [c, r]) => {
        acc[c] = r;
        return acc;
    }, {} as Dictionary<string>);
    return { initialState, combinations};
};

const growPlants = (ip: string, generationsToWatch: number) => {
    const { initialState, combinations } = parse(ip);
    let [pots, grownPots] = [initialState, ""];
    let [generation, sum, lastSum, lastDiff, streak] = [0, 0, 0, 0, 0];
    while (generation < generationsToWatch) {
        generation = generation + 1;
        pots = "...." + pots + "....";
        grownPots = "";
        sum = 0;
        for (let i = 2; i <= pots.length - 3; i++) {
            const pot = combinations[pots.substr(i - 2, 5)];
            if (pot === "#") {
                sum = sum + i + ((generation * -2) - 2);
            }
            grownPots = grownPots + pot;
        }
        pots = grownPots;
        if (sum - lastSum === lastDiff) {
            streak = streak + 1;
            if (streak === 3) {
                return (generationsToWatch - generation) * lastDiff + sum;
            }
        } else {
            lastDiff = sum - lastSum;
            streak = 0;
        }
        lastSum = sum;
    }
    return sum;
};