107 lines
2.2 KiB
Go
107 lines
2.2 KiB
Go
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package main
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import (
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"fmt"
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"os"
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"strings"
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"github.com/kelindar/bitmap"
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)
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func readLines(filename string) []string {
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raw, err := os.ReadFile(filename)
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if err != nil {
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panic(err)
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}
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return strings.Split(string(raw), "\n")
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}
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func main() {
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filename := "input0.txt"
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if len(os.Args) > 1 {
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filename = os.Args[1]
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}
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lines := readLines(filename)
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m := parseManifold(lines)
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_, splits := m.eval()
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fmt.Printf("%v\n", splits)
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fmt.Printf("%v\n", m.quantumEval())
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}
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type manifold struct {
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width uint32
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source bitmap.Bitmap
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splitters []bitmap.Bitmap
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}
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func (m *manifold) eval() (bitmap.Bitmap, uint64) {
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splits := uint64(0)
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active := m.source.Clone(nil)
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for _, splitter := range m.splitters {
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activated := active.Clone(nil)
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activated.And(splitter)
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var produced bitmap.Bitmap
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activated.Range(func(i uint32) {
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splits++
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produced.Set(i - 1)
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produced.Set(i + 1)
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})
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active.AndNot(activated)
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active.Or(produced)
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}
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return active, splits
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}
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// set expansion is just too slow
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// instead, work like eval but use a slice of uints where the
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// values are the number of timelines that produce a tachyon
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// at a given position; when a tachyon is split and joins
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// an existing one, we increment, not just bitwise or.
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// the total is the sum of all timelines of all positions
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// in the final frame.
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// 3141808011 is too low
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func (m *manifold) quantumEval() uint64 {
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active := make([]uint64, m.width)
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m.source.Range(func(i uint32) {
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active[i] = 1
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})
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for _, frame := range m.splitters {
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next := make([]uint64, m.width)
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copy(next, active)
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for i, t := range active {
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if t == 0 {
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continue
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}
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splitter := frame.Contains(uint32(i))
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if splitter {
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next[i] = 0
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next[i-1] += t
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next[i+1] += t
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}
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}
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active = next
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}
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total := uint64(0)
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for _, x := range active {
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total += x
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}
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return total
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}
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func parseManifold(lines []string) *manifold {
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var m manifold
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m.width = uint32(len(lines[0]))
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m.source.Set(uint32(strings.Index(lines[0], "S")))
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for i := 1; i < len(lines); i++ {
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var splitter bitmap.Bitmap
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for j, c := range lines[i] {
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if c == '^' {
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splitter.Set(uint32(j))
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}
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}
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m.splitters = append(m.splitters, splitter)
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}
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return &m
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}
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