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Simplify D6P2 Kotlin further

This commit is contained in:
kageru 2019-12-06 11:44:33 +01:00
parent 9396c143d3
commit 687cba82dd
1 changed files with 2 additions and 13 deletions
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15
2019/06/day06.kt
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@ -1,12 +1,12 @@
fun main() {
val input = generateSequence(::readLine).map { it.split(")") }.toList()
val parentToChildren = input.groupBy { it[0] }.mapValues { it.value.map { it[1] } }
val childToParent = input.associateBy { it[1] }.mapValues { it.value[0] }
val rootNode = (parentToChildren.keys - parentToChildren.values.flatten().toSet()).first()
println("Part 1: ${countOrbiters(parentToChildren, rootNode, 0)}")
val childToParent = input.associateBy { it[1] }.mapValues { it.value[0] }
val santaParents = getParents(childToParent, "SAN")
val myParents = getParents(childToParent, "YOU")
val commonParent = firstCommon(santaParents, myParents)
val commonParent = santaParents.first { it in myParents }
println("Part 2: ${santaParents.indexOf(commonParent) + myParents.indexOf(commonParent)}")
}
@ -15,14 +15,3 @@ fun <T> countOrbiters(graph: Map<T, List<T>>, key: T, acc: Int): Int =
fun <T> getParents(graph: Map<T, T>, key: T): List<T> =
graph[key]?.let { curr -> listOf(curr) + getParents(graph, curr) } ?: emptyList()
fun <T> firstCommon(first: List<T>, second: List<T>): T {
val seen = mutableSetOf<T>()
for (i in 0..first.size) {
if (first[i] in seen) return first[i]
seen.add(first[i])
if (second[i] in seen) return second[i]
seen.add(second[i])
}
error("should be unreachable")
}