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main.go
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main.go
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package main
import (
"fmt"
"io"
"os"
"github.com/devries/advent_of_code_2022/utils"
"github.com/spf13/pflag"
)
const inputfile = "../inputs/day03.txt"
func main() {
pflag.Parse()
f, err := os.Open(inputfile)
utils.Check(err, "error opening input")
defer f.Close()
r := solve(f)
fmt.Println(r)
}
func solve(r io.Reader) int {
lines := utils.ReadLines(r)
groupSize := 3
var pSum int
for i := 0; i < len(lines); i += groupSize {
groupLines := lines[i : i+groupSize]
var itemSet uint64 = 0xfffffffffffff
for _, ln := range groupLines {
bm := bitmask([]rune(ln))
itemSet &= bm
}
pSum += maskToPriority(itemSet)
}
return pSum
}
func priority(c rune) int {
if c >= 'a' && c <= 'z' {
return int(c - 'a' + 1)
} else {
return int(c - 'A' + 27)
}
}
func bitmask(letters []rune) uint64 {
var ret uint64
for _, c := range letters {
ret |= 1 << (priority(c) - 1)
}
return ret
}
func maskToPriority(v uint64) int {
var ret int
for l := v; l > 0; l >>= 1 {
ret++
}
return ret
}