1+ package adventofcode2023
2+
3+ import java.io.File
4+ import java.util.LinkedList
5+
6+ object Day20 {
7+ private const val BROADCASTER = " broadcaster"
8+ private const val RX_OUTPUT = " rx"
9+
10+ private val inputs = File (" resources/adventofcode2023/Day20.txt"
11+ .readLines()
12+ .map { line ->
13+ val split = line.split(" -> "
14+ Pair (split[0 ], split[1 ].split(" , "
15+ }
16+
17+ private val modules: Map <String , Module > = inputs.associate { line ->
18+ val name = line.first.removePrefix(" %" " &"
19+ val module =
20+ when (line.first.first()) {
21+ ' %' -> FlipFlopModule (line.second)
22+ ' &' -> ConjunctionModule (line.second, inputs.filter { it.second.contains(name) }.map {
23+ it.first.removePrefix(" %" " &"
24+ })
25+ else -> BroadcastModule (line.second)
26+ }
27+ name to module
28+ }
29+
30+ private sealed class Module (val outputs : List <String >) {
31+ abstract fun send (pulse : Boolean , input : String ): Map <String , Boolean >
32+
33+ open fun reset () {}
34+ }
35+
36+ private class BroadcastModule (outputs : List <String >) : Module(outputs) {
37+ override fun send (pulse : Boolean , input : String ): Map <String , Boolean > =
38+ outputs.associateWith { pulse }
39+ }
40+
41+ private class FlipFlopModule (outputs : List <String >) : Module(outputs) {
42+ var enabled = false
43+
44+ override fun send (pulse : Boolean , input : String ): Map <String , Boolean > =
45+ if (pulse) emptyMap()
46+ else {
47+ enabled = ! enabled
48+ outputs.associateWith { enabled }
49+ }
50+
51+ override fun reset () { enabled = false }
52+ }
53+
54+ private class ConjunctionModule (outputs : List <String >, val inputs : List <String >) : Module(outputs) {
55+ var lastPulses = inputs.associateWith { false }.toMutableMap()
56+
57+ override fun send (pulse : Boolean , input : String ): Map <String , Boolean > {
58+ lastPulses[input] = pulse
59+ return outputs.associateWith { ! lastPulses.values.all { it } }
60+ }
61+
62+ override fun reset () { lastPulses = inputs.associateWith { false }.toMutableMap() }
63+ }
64+
65+ private fun pushButton (onEveryPulse : (String , Boolean , String ) -> Unit ) {
66+ val queue = LinkedList (listOf (Triple (BROADCASTER , false , " "
67+
68+ while (queue.isNotEmpty()) {
69+ val (destination, pulse, from) = queue.removeFirst()
70+ val module = modules[destination]
71+
72+ onEveryPulse(destination, pulse, from)
73+
74+ module?.send(pulse, from)?.forEach {
75+ queue.add(Triple (it.key, it.value, destination))
76+ }
77+ }
78+ }
79+
80+ private fun highLowPulsesCounts (times : Int ): Map <Boolean , Long > {
81+ val pulseCount = mutableMapOf (true to 0L , false to 0L )
82+
83+ for (i in 1 .. times) {
84+ pushButton { _, pulse, _ ->
85+ pulseCount[pulse] = pulseCount[pulse]!! .plus(1 )
86+ }
87+ }
88+
89+ return pulseCount
90+ }
91+
92+ private fun pushesToGetRx (): Long {
93+ val beforeRxName = modules.filter { it.value.outputs.contains(RX_OUTPUT ) }.map { it.key }.single()
94+ val beforeRxInputsCounts = modules.filter { it.value.outputs.contains(beforeRxName) }.mapValues { 0L }.toMutableMap()
95+ var pushCount = 0L
96+
97+ while (beforeRxInputsCounts.any { it.value == 0L }) {
98+ pushCount++
99+
100+ pushButton { destination, pulse, from ->
101+ if (destination == beforeRxName && pulse) {
102+ beforeRxInputsCounts[from] = pushCount
103+ }
104+ }
105+ }
106+
107+ return beforeRxInputsCounts.values.reduce { acc, i -> lcm(acc, i) }
108+ }
109+
110+ private fun gcd (a : Long , b : Long ): Long = if (b == 0L ) a else gcd(b, a % b)
111+
112+ private fun lcm (a : Long , b : Long ): Long = a * b / gcd(a, b)
113+
114+ fun resetModules () = modules.forEach { it.value.reset() }
115+
116+ fun part1 () = println (highLowPulsesCounts(1000 ).values.reduce { acc, i -> acc * i })
117+
118+ fun part2 () = println (pushesToGetRx())
119+ }
120+
121+ fun main () {
122+ Day20 .part1()
123+ Day20 .resetModules()
124+ Day20 .part2()
125+ }
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