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@pseale
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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