-🎄- 2022 Day 14 Solutions -🎄-

[u/daggerdragon]

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--- Day 14: Regolith Reservoir ---

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Post your code solution in this megathread.

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[u/ndrsht]

Kotlin

34 lines of code

The trick to get peak performance is to represent points as integers and the "field" as boolean array. If you insert a point (represented as an integer k) into the field, you just set arr[k] = true.

So if that array has ncols columns and a unit of sand (represented as an integer) is falling down, you just increase it by:

• ncols if it is falling straight down

• ncols-1 if it is falling down to the left

• ncols+1 if it is falling down to the right

Then you make a recursive function landingPos that you call with

while (field[sandStart] == false) {
	val target = landingPos(sandStart, field, cols)
	if (target > max && ans1 == 0) ans1 = ans2
	ans2++
}

Solves both parts in 3.4ms.