1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
import kotlin.collections.ArrayDeque
sealed class Packet(
private val bits: Int,
protected val version: Int,
) {
class Literal(
bits: Int,
version: Int,
private val literalValue: Long,
) : Packet(bits, version) {
override fun versionSum(): Int = version
override val value: Long
get() = literalValue
}
class Operator(
bits: Int,
version: Int,
private val typeId: Int,
private val subpackets: List<Packet>,
) : Packet(bits, version) {
override fun versionSum(): Int = version + subpackets.sumOf { it.versionSum() }
override val value: Long
get() = when (typeId) {
0 -> subpackets.sumOf { it.value }
1 -> subpackets.fold(1) { acc, packet -> acc * packet.value }
2 -> subpackets.minOf { it.value }
3 -> subpackets.maxOf { it.value }
5, 6, 7 -> {
val (first, second) = subpackets.map { it.value }
if (when (typeId) {
5 -> first > second
6 -> first < second
7 -> first == second
else -> false
}) {
1
} else {
0
}
}
else -> throw IllegalStateException("Illegal packet type id.")
}
}
abstract fun versionSum(): Int
abstract val value: Long
companion object {
fun parse(bitQueue: ArrayDeque<Char>): Packet {
var packetBits = 0
fun takeBits(n: Int): Int {
packetBits += n
return (0 until n)
.joinToString("") { bitQueue.removeFirst().toString() }
.toInt(2)
}
val version = takeBits(3)
when (val typeId = takeBits(3)) {
4 -> { // Literal packet
var literalValue = 0L
while (true) {
val groupHeader = takeBits(1)
val groupValue = takeBits(4)
literalValue = (literalValue shl 4) + groupValue
if (groupHeader == 0) {
break
}
}
return Literal(packetBits, version, literalValue)
}
else -> { // Operator packet
val subpackets = mutableListOf<Packet>()
when (takeBits(1)) {
0 -> {
val subpacketLength = takeBits(15)
var currentSubpacketLength = 0
while (currentSubpacketLength < subpacketLength) {
val subpacket = parse(bitQueue)
currentSubpacketLength += subpacket.bits
subpackets.add(subpacket)
}
}
1 -> {
val subpacketCount = takeBits(11)
repeat(subpacketCount) {
subpackets.add(parse(bitQueue))
}
}
else -> throw IllegalStateException("Illegal length type id.")
}
packetBits += subpackets.sumOf { it.bits }
return Operator(packetBits, version, typeId, subpackets)
}
}
}
}
}
fun main() {
fun parse(input: String): Packet {
val bitQueue = ArrayDeque(
input
.flatMap {
it
.toString()
.toInt(16)
.toString(2)
.padStart(4, '0')
.toList()
}
)
return Packet.parse(bitQueue)
}
fun part1(input: String): Int = parse(input).versionSum()
fun part2(input: String): Long = parse(input).value
check(part1("8A004A801A8002F478") == 16)
check(part1("620080001611562C8802118E34") == 12)
check(part1("C0015000016115A2E0802F182340") == 23)
check(part1("A0016C880162017C3686B18A3D4780") == 31)
check(part2("C200B40A82") == 3L)
check(part2("04005AC33890") == 54L)
check(part2("880086C3E88112") == 7L)
check(part2("CE00C43D881120") == 9L)
check(part2("D8005AC2A8F0") == 1L)
check(part2("F600BC2D8F") == 0L)
check(part2("9C005AC2F8F0") == 0L)
check(part2("9C0141080250320F1802104A08") == 1L)
val input = readInputAsString("Day16")
println(part1(input))
println(part2(input))
}
|
