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68 lines
1.1 KiB
68 lines
1.1 KiB
package main
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import (
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"bufio"
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"bytes"
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"fmt"
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"io"
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"unicode"
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)
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type nextlocation struct {
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left string
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right string
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}
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func readsteps(b *bufio.Reader) []byte {
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steps, err := b.ReadBytes('\n')
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must(err)
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return bytes.TrimFunc(steps, unicode.IsSpace)
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}
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type day08 struct{}
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func (d day08) solve1(r io.Reader) string {
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iterations := 0
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current := "AAA"
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buf := bufio.NewReader(r)
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steps := readsteps(buf)
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_, err := buf.ReadBytes('\n')
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must(err)
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m := make(map[string]nextlocation)
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for next := true; next; {
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line, err := buf.ReadBytes('(')
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must(err)
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location := string(line[:3])
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left, err := buf.ReadBytes(',')
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must(err)
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remaining, err := buf.ReadBytes('\n')
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next = !reachedeof(err)
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nextlocation := nextlocation{
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left: string(bytes.Trim(left, ",")),
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right: string(remaining[1:4]),
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}
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m[location] = nextlocation
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}
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for ; current != "ZZZ"; iterations++ {
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step := steps[iterations%len(steps)]
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if step == 'R' {
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current = m[current].right
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} else {
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current = m[current].left
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}
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}
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return fmt.Sprintf("%d", iterations)
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}
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func (d day08) solve2(r io.Reader) string {
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return "incomplete"
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}
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