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Day12.kt
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Day12.kt
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import java.util.LinkedList
import java.util.Queue
fun main() {
fun solve(input: List<String>, part1: Boolean): Int {
fun value(ch: Char) = when (ch) {
'S' -> 'a'
'E' -> 'z'
else -> ch
}
val visited = mutableSetOf<Pair<Int, Int>>()
val q: Queue<Triple<Int, Int, Int>> = LinkedList()
for (i in input.indices)
for (j in input[0].indices)
if ((part1 && input[i][j] == 'S') || (!part1 && value(input[i][j]) == 'a'))
q.add(Triple(i, j, 0))
while (q.isNotEmpty()) {
val (x, y, c) = q.poll()
if (x to y in visited)
continue
visited += x to y
if (input[x][y] == 'E')
return c
listOf(-1 to 0, 0 to 1, 1 to 0, 0 to -1).forEach { (dx, dy) ->
val (a, b) = (x + dx) to (y + dy)
if (a in input.indices && b in input[0].indices && value(input[a][b]) - value(input[x][y]) < 2)
q.add(Triple(a, b, c + 1))
}
}
return -1
}
fun part1(input: List<String>) = solve(input, part1 = true)
fun part2(input: List<String>) = solve(input, part1 = false)
val testInput = readInputLines("Day12_test")
check(part1(testInput) == 31)
check(part2(testInput) == 29)
val input = readInputLines("Day12")
println(part1(input))
println(part2(input))
}