AdventJS - Challenge #9: Crazy Xmas lights
A company that manufactures Christmas lights has asked us to help them.
They have led strips that are like an Array. Each position is a led and can be on (1) or off (0).
Every 7 seconds, the leds change state in this way:
- If the led is off, it turns on if the led on its left (index - 1) was on before.
- If the led is on, it remains on.
- They asked us for a program that tells us how many seconds it takes for all the leds to turn on. The seconds are expressed as an integer. For example:
const leds = [0, 1, 1, 0, 1]
countTime(leds) // 7
// 7 seconds because in the first change
// all the lights turned on
// 0s: [0, 1, 1, 0, 1]
// 7s: [1, 1, 1, 1, 1]
countTime([0, 0, 0, 1]) // 21
// 21 seconds because it needs three changes:
// 0s: [0, 0, 0, 1]
// 7s: [1, 0, 0, 1]
// 14s: [1, 1, 0, 1]
// 21s: [1, 1, 1, 1]
countTime([0, 0, 1, 0, 0]) // 28
// 28 seconds because it needs four changes:
// 0s: [0, 0, 1, 0, 0]
// 7s: [0, 0, 1, 1, 0]
// 14s: [0, 0, 1, 1, 1]
// 21s: [1, 0, 1, 1, 1]
// 28s: [1, 1, 1, 1, 1]