Created
December 28, 2016 06:18
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import _ = require("lodash") | |
let input = `Disc #1 has 13 positions; at time=0, it is at position 11. | |
Disc #2 has 5 positions; at time=0, it is at position 0. | |
Disc #3 has 17 positions; at time=0, it is at position 11. | |
Disc #4 has 3 positions; at time=0, it is at position 0. | |
Disc #5 has 7 positions; at time=0, it is at position 2. | |
Disc #6 has 19 positions; at time=0, it is at position 17.` | |
interface Disc { | |
positions: number, | |
startingPosition: number, | |
timeOffset: number | |
} | |
function parse(line: string, timeOffset: number): Disc { | |
const matches = /has (\d+) positions; at time=0, it is at position (\d+)\.$/.exec(line) | |
return { | |
positions: Number(matches[1]), | |
startingPosition: Number(matches[2]), | |
timeOffset: timeOffset | |
} | |
} | |
function wouldSlipThrough(disc: Disc, time: number): boolean { | |
const position = disc.startingPosition + time + disc.timeOffset | |
return (position % disc.positions) === 0 | |
} | |
let discsHaveBeenRearranged = true // Part A / Part B differentiator | |
function run(): void { | |
const lines = input.split("\n") | |
let discs = _.range(0, lines.length).map(i => parse(lines[i], i)) | |
if (discsHaveBeenRearranged) { | |
discs = discs.concat({positions: 11, startingPosition: 0, timeOffset: discs.length }) | |
} | |
let time = 0 | |
while (true) { | |
if (_.range(0, discs.length).every(i => wouldSlipThrough(discs[i], time + 1))) { | |
console.log(`Everything lines up at time=${time}`) | |
break | |
} | |
time++ | |
} | |
} |
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