Advent of Code 2018: Day 12
Part 1 After 20 generations, what is the sum of the numbers of all pots which contain a plant?
function* evolve () { let offset = 0; let state = startState; while (true) { state = '.....' + state + '.....'; offset += 3; let nextState = []; for (let i = 2; i < state.length - 2; i++) { let window = state.slice(i-2, i+3); nextState.push(rules[window] || state[i]); } while (nextState[0] === '.') { nextState = nextState.slice(1); offset -= 1; } while (nextState[nextState.length - 1] === '.') { nextState = nextState.slice(0, -1); } state = nextState.join(''); yield [state, offset]; } }
function sumPotIndices (state, offset) { let out = 0; for (let i = 0; i < state.length; i++) { if (state[i] === '#') { out += (i - offset); } } return out; }
part1Sum = { const gen = evolve(); let state, offset; for (let g = 1; g <= 20; g++) { [state, offset] = gen.next().value; } return sumPotIndices(state, offset); }
Part 2 After fifty billion (50000000000) generations, what is the sum of the numbers of all pots which contain a plant?
timeSeries = { let gen = evolve(); let d = []; for (let t = 1; t < 1000; t += 1) { let sum = sumPotIndices(...gen.next().value); d.push({'generation': t, 'sum': sum}); } return d; }
vegalite({ data: {values: timeSeries}, mark: {type: "line", interpolate: "step"}, width, height: 360, autosize: "fit", encoding: { x: { field: "generation", type: "quantitative" }, y: { field: "sum", type: "quantitative" } } })
part2Sum = { const gen = evolve(); const numGenerations = 50000000000; let prevSum = 0; let prevDifference; let repeatCount = 0; for (let g = 1; g <= numGenerations; g += 1) { const sum = sumPotIndices(...gen.next().value); if (sum - prevSum === prevDifference) { repeatCount++; if (repeatCount > 10) { return (sum + (numGenerations - g) * prevDifference); } } else { prevDifference = sum - prevSum; prevSum = sum; } } }
startState = '##....#.#.#...#.#..#.#####.#.#.##.#.#.#######...#.##....#..##....#.#..##.####.#..........#..#...#'
rules = { let out = {}; for (let line of rulesInput.split('\n')) { let [key, value] = line.split(' => '); out[key] = value; } return out; }
rulesInput=`..#.# => # .#### => # #.... => . ####. => # ...## => . .#.#. => . ..#.. => . ##.#. => . #.#.# => # ..... => . #.#.. => . ....# => . .#..# => . ###.# => # #..#. => . ##### => . ...#. => # #.##. => # .#.## => # #..## => # .##.. => # ##.## => . ..### => . ###.. => . ##..# => # .#... => # .###. => # #.### => . .##.# => . #...# => # ##... => . ..##. => .`
vegalite = require("@observablehq/vega-lite@0.1")