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| 1 | package main | |
| 2 | ||
| 3 | import ( | |
| 4 | "aoc/utils" | |
| 5 | "fmt" | |
| 6 | "strings" | |
| 7 | ) | |
| 8 | ||
| 9 | func main() {
| |
| 10 | g := NewGraph(utils.ReadLines()) | |
| 11 | fmt.Println("part1: ", g.Part1())
| |
| 12 | fmt.Println("part2: ", g.Part2())
| |
| 13 | } | |
| 14 | ||
| 15 | type Graph struct {
| |
| 16 | edges [][]uint16 | |
| 17 | bigCaves uint16 | |
| 18 | } | |
| 19 | ||
| 20 | func (g *Graph) Part1() int {
| |
| 21 | initCache() | |
| 22 | return g.countPathsPart1(startCave, 0) | |
| 23 | } | |
| 24 | ||
| 25 | func (g *Graph) Part2() int {
| |
| 26 | initCache() | |
| 27 | return g.countPathsPart2(startCave, 0) | |
| 28 | } | |
| 29 | ||
| 30 | const ( | |
| 31 | startCave = 1 | |
| 32 | endCave = 0 | |
| 33 | ) | |
| 34 | ||
| 35 | func caveMask(cave uint16) uint16 {
| |
| 36 | return 1 << cave | |
| 37 | } | |
| 38 | ||
| 39 | func (g *Graph) countPathsPart1(from uint16, visited uint16) int {
| |
| 40 | var count int | |
| 41 | if count, ok := getCachedResult(from, visited); ok {
| |
| 42 | return count | |
| 43 | } | |
| 44 | for _, to := range g.edges[from] {
| |
| 45 | if to == endCave {
| |
| 46 | count++ | |
| 47 | continue | |
| 48 | } | |
| 49 | toMask := caveMask(to) &^ g.bigCaves | |
| 50 | if visited&toMask == 0 {
| |
| 51 | count += g.countPathsPart1(to, visited|toMask) | |
| 52 | } | |
| 53 | } | |
| 54 | putToCache(from, visited, count) | |
| 55 | return count | |
| 56 | } | |
| 57 | ||
| 58 | const doubleMask = 1 << 15 | |
| 59 | ||
| 60 | func (g *Graph) countPathsPart2(from uint16, visited uint16) int {
| |
| 61 | var count int | |
| 62 | if count, ok := getCachedResult(from, visited); ok {
| |
| 63 | return count | |
| 64 | } | |
| 65 | for _, to := range g.edges[from] {
| |
| 66 | if to == endCave {
| |
| 67 | count++ | |
| 68 | continue | |
| 69 | } | |
| 70 | toMask := caveMask(to) &^ g.bigCaves | |
| 71 | if visited&toMask == 0 {
| |
| 72 | count += g.countPathsPart2(to, visited|toMask) | |
| 73 | } else if visited&doubleMask == 0 {
| |
| 74 | count += g.countPathsPart2(to, visited|doubleMask) | |
| 75 | } | |
| 76 | } | |
| 77 | putToCache(from, visited, count) | |
| 78 | return count | |
| 79 | } | |
| 80 | ||
| 81 | // Memoïzation | |
| 82 | ||
| 83 | type key struct {
| |
| 84 | cave uint16 | |
| 85 | visited uint16 | |
| 86 | } | |
| 87 | ||
| 88 | type cache map[key]int | |
| 89 | ||
| 90 | var memo cache | |
| 91 | ||
| 92 | func initCache() {
| |
| 93 | - | memo = make(cache) |
| 93 | + | memo = make(cache, 500) |
| 94 | } | |
| 95 | ||
| 96 | func getCachedResult(from uint16, visited uint16) (int, bool) {
| |
| 97 | count, ok := memo[key{from, visited}]
| |
| 98 | return count, ok | |
| 99 | } | |
| 100 | ||
| 101 | func putToCache(from uint16, visited uint16, count int) {
| |
| 102 | memo[key{from, visited}] = count
| |
| 103 | } | |
| 104 | ||
| 105 | // Input parsing | |
| 106 | ||
| 107 | func NewGraph(input []string) *Graph {
| |
| 108 | g := newBuilder() | |
| 109 | g.parse(input) | |
| 110 | return &g.Graph | |
| 111 | } | |
| 112 | ||
| 113 | func newBuilder() *graphBuilder {
| |
| 114 | return &graphBuilder{
| |
| 115 | Graph: Graph{edges: make([][]uint16, 2, 16)},
| |
| 116 | caves: map[string]uint16{
| |
| 117 | "start": startCave, | |
| 118 | "end": endCave, | |
| 119 | }, | |
| 120 | } | |
| 121 | } | |
| 122 | ||
| 123 | type graphBuilder struct {
| |
| 124 | Graph | |
| 125 | caves map[string]uint16 | |
| 126 | } | |
| 127 | ||
| 128 | func (g *graphBuilder) parse(input []string) {
| |
| 129 | for _, line := range input {
| |
| 130 | edge := strings.Split(line, "-") | |
| 131 | c1 := g.getCave(edge[0]) | |
| 132 | c2 := g.getCave(edge[1]) | |
| 133 | g.addEdge(c1, c2) | |
| 134 | } | |
| 135 | } | |
| 136 | ||
| 137 | func (g *graphBuilder) addEdge(c1, c2 uint16) {
| |
| 138 | if c1 != endCave && c2 != startCave {
| |
| 139 | g.edges[c1] = append(g.edges[c1], c2) | |
| 140 | } | |
| 141 | if c1 != startCave && c2 != endCave {
| |
| 142 | g.edges[c2] = append(g.edges[c2], c1) | |
| 143 | } | |
| 144 | } | |
| 145 | ||
| 146 | func (g *graphBuilder) getCave(name string) uint16 {
| |
| 147 | if cave, ok := g.caves[name]; ok {
| |
| 148 | return cave | |
| 149 | } | |
| 150 | cave := uint16(len(g.caves)) | |
| 151 | g.caves[name] = cave | |
| 152 | - | if 'A' <= name[0] && name[0] < 'Z' {
|
| 152 | + | if 'A' <= name[0] && name[0] <= 'Z' {
|
| 153 | g.bigCaves |= caveMask(cave) | |
| 154 | } | |
| 155 | g.edges = append(g.edges, nil) | |
| 156 | return cave | |
| 157 | } | |
| 158 |
