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Day 8 revisited: Replaced manual prime factorization by new gcd and lcm toolset.

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This commit is contained in:
Chris Hodges 2023-12-09 06:50:32 +01:00
parent f026dfb6de
commit 4c922f356d
2 changed files with 39 additions and 30 deletions
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7
src/Utils.kt
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@ -2,6 +2,13 @@ import java.io.File
import java.math.BigInteger import java.math.BigInteger
import java.security.MessageDigest import java.security.MessageDigest
fun Int.gcd(b: Int): Int = if (b == 0) this else b.gcd(this % b)
fun Long.gcd(b: Long): Long = if (b == 0L) this else b.gcd(this % b)
fun Int.lcm(b: Int): Int = this / gcd(b) * b
fun Long.lcm(b: Long): Long = this / gcd(b) * b
fun Iterable<Int>.lcm(): Int = reduce(Int::lcm)
fun Iterable<Long>.lcm(): Long = reduce(Long::lcm)
/** /**
* Reads lines from the given input txt file. * Reads lines from the given input txt file.
*/ */

62
src/aoc2023/Day08.kt
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@ -1,5 +1,6 @@
package aoc2023 package aoc2023
import lcm
import println import println
import readInput import readInput
@ -95,36 +96,37 @@ XXX = (XXX, XXX)
} while (!loc.endsWith("Z")) } while (!loc.endsWith("Z"))
ggts.add(steps) ggts.add(steps)
} }
val primes = ArrayList<Int>() return ggts.map(Int::toLong).lcm()
val factors = HashSet<Int>() // val primes = ArrayList<Int>()
var prime = 2 // val factors = HashSet<Int>()
primes.add(2) // var prime = 2
do { // primes.add(2)
val newGgts = HashSet<Int>() // do {
for (f in ggts) { // val newGgts = HashSet<Int>()
if (prime * 2 - 1 > f) { // for (f in ggts) {
factors.add(f) // if (prime * 2 - 1 > f) {
} else { // factors.add(f)
if (f % prime == 0) { // } else {
newGgts.add(f / prime) // if (f % prime == 0) {
factors.add(prime) // newGgts.add(f / prime)
} else { // factors.add(prime)
newGgts.add(f) // } else {
} // newGgts.add(f)
} // }
} // }
ggts = newGgts // }
if (prime == 2) { // ggts = newGgts
prime = 3 // if (prime == 2) {
} else { // prime = 3
do { // } else {
prime += 2 // do {
} while (primes.any { (prime % it) == 0 }) // prime += 2
} // } while (primes.any { (prime % it) == 0 })
primes.add(prime) // }
} while (ggts.isNotEmpty()) // primes.add(prime)
// } while (ggts.isNotEmpty())
return factors.map { it.toLong() }.reduce(Long::times) //
// return factors.map { it.toLong() }.reduce(Long::times)
} }
// test if implementation meets criteria from the description, like: // test if implementation meets criteria from the description, like: