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package main
import (
"fmt"
"log"
"os"
)
func inside(c byte, b []byte) int {
for i, a := range b {
if c == a {
return i
}
}
return -1
}
func packetMarker(buf []byte, l int) int {
i, j := 0, 1
for (j - i) < l {
n := inside(buf[j], buf[i:j])
if n != -1 {
i += n + 1
} else {
j++
}
}
return j
}
func main() {
f, err := os.Open("day6.txt")
if err != nil {
log.Fatal("Could not open input file", err)
}
buf := make([]byte, 32*1024)
_, err = f.Read(buf)
if err != nil {
log.Fatal("Got error reading into buffer", err)
}
// Part 1
r := packetMarker(buf, 4)
fmt.Println("Part 1", r, string(buf[r-4:r]))
// Part 2
r = packetMarker(buf, 14)
fmt.Println("Part 2", r, string(buf[r-14:r]))
}
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