advent-of-code/2021
advent-of-code/2021
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day(09): refactor

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- introduce ‹validAdjacentIndices›
- clean up DFS
- remove debugging println
- fix bug of mapping over values instead of indices

Signed-off-by: Matej Focko <mfocko@redhat.com>
This commit is contained in:
Matej Focko 2021-12-09 06:46:32 +01:00
parent 28f318fbed
commit 1cfee94e2a
1 changed files with 14 additions and 21 deletions
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33
src/year2021/day09/Day09.kt
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@ -3,39 +3,34 @@ package year2021.day09
import readInput import readInput
import kotlin.math.max import kotlin.math.max
fun getRiskLevel(input: List<List<Int>>, y: Int, x: Int): Int = listOf( fun validAdjacentIndices(input: List<List<Int>>, y: Int, x: Int): Iterable<Pair<Int, Int>> = listOf(
Pair(y - 1, x), Pair(y - 1, x),
Pair(y + 1, x), Pair(y + 1, x),
Pair(y, x + 1), Pair(y, x + 1),
Pair(y, x - 1) Pair(y, x - 1)
).filter { (y0, x0) -> y0 >= 0 && y0 < input.size && x0 >= 0 && x0 < input[y0].size } ).filter { (y0, x0) -> y0 >= 0 && y0 < input.size && x0 >= 0 && x0 < input[y0].size }
fun getRiskLevel(input: List<List<Int>>, y: Int, x: Int): Int = validAdjacentIndices(input, y, x)
.map { (y0, x0) -> input[y0][x0] } .map { (y0, x0) -> input[y0][x0] }
.all { it > input[y][x] }.let { isLowPoint -> if (isLowPoint) input[y][x] + 1 else 0 } .all { it > input[y][x] }
.let { isLowPoint -> if (isLowPoint) input[y][x] + 1 else 0 }
fun part1(input: List<List<Int>>): Int = input fun part1(input: List<List<Int>>): Int = input
.mapIndexed { y, row -> .mapIndexed { y, row ->
row.mapIndexed { x, col -> row.indices.map { x ->
getRiskLevel(input, y, x) getRiskLevel(input, y, x)
} }
}.sumOf { row -> row.sum() } }.sumOf { row -> row.sum() }
fun dfs(input: MutableList<MutableList<Int>>, y: Int, x: Int): Int { fun dfs(input: MutableList<MutableList<Int>>, y: Int, x: Int): Int = when (input[y][x]) {
if (input[y][x] != 0) { 0 -> {
return 0 // mark as visited
}
input[y][x] = -1 input[y][x] = -1
var total = 1 // check adjacent
listOf( 1 + validAdjacentIndices(input, y, x).sumOf { (y0, x0) -> dfs(input, y0, x0) }
Pair(y - 1, x), }
Pair(y + 1, x), else -> 0
Pair(y, x + 1),
Pair(y, x - 1)
).filter { (y0, x0) -> y0 >= 0 && y0 < input.size && x0 >= 0 && x0 < input[y0].size }
.forEach { (y0, x0) -> total += dfs(input, y0, x0) }
return total;
} }
fun part2(input: List<List<Int>>): Int { fun part2(input: List<List<Int>>): Int {
@ -56,8 +51,6 @@ fun part2(input: List<List<Int>>): Int {
} }
sizes.sortDescending() sizes.sortDescending()
println(sizes)
return sizes.take(3).fold(1) { product, n -> n * product } return sizes.take(3).fold(1) { product, n -> n * product }
} }