advent-of-code/aoc2023/day15/main.go

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package main
import (
"bufio"
_ "embed"
"fmt"
"slices"
"strings"
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aoc "go.sour.is/advent-of-code"
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)
var log = aoc.Log
func main() { aoc.MustResult(aoc.Runner(run)) }
type result struct {
valuePT1 int
valuePT2 int
}
func (r result) String() string { return fmt.Sprintf("%#v", r) }
func run(scan *bufio.Scanner) (*result, error) {
r := &result{}
var ops []string
for scan.Scan() {
text := scan.Text()
ops = strings.Split(text, ",")
r.valuePT1 = aoc.Reduce(func(i int, t string, sum int) int {
sum += hash(t)
return sum
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}, 0, slices.Values(ops))
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}
var boxen boxes
boxen = aoc.Reduce(func(i int, op string, b boxes) boxes {
return b.Op(op)
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}, boxen, slices.Values(ops))
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r.valuePT2 = boxen.Sum()
log(boxen)
return r, nil
}
func hash(s string) int {
var sum int
for _, a := range s {
sum += int(a)
sum *= 17
sum %= 256
}
return sum
}
type lens struct {
label string
value int
}
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func (l lens) String() string {
return fmt.Sprintf("[%s %d]", l.label, l.value)
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}
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type box []lens
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func (lis box) String() string {
var buf strings.Builder
if len(lis) > 0 {
buf.WriteString(lis[0].String())
}
for _, l := range lis[1:] {
buf.WriteString(l.String())
}
return buf.String()
}
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type boxes [256]box
func (lis boxes) String() string {
var buf strings.Builder
buf.WriteString("Boxes:\n")
for i, b := range lis {
if len(b) > 0 {
fmt.Fprintf(&buf, "Box %d: %v\n", i, b)
}
}
return buf.String()
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}
func (lis boxes) Op(op string) boxes {
if a, _, ok := strings.Cut(op, "-"); ok {
i := hash(a)
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pos := slices.IndexFunc(lis[i], func(l lens) bool { return l.label == a })
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if pos >= 0 {
lis[i] = append(lis[i][:pos], lis[i][pos+1:]...)
}
} else if a, b, ok := strings.Cut(op, "="); ok {
i := hash(a)
v := aoc.Atoi(b)
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pos := slices.IndexFunc(lis[i], func(l lens) bool { return l.label == a })
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if pos == -1 {
lis[i] = append(lis[i], lens{a, v})
} else {
lis[i][pos].value = v
}
}
return lis
}
func (lis boxes) Sum() int {
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// return aoc.Reduce(func(b int, box box, sum int) int {
// return aoc.Reduce(
// func(s int, lens lens, sum int) int {
// return sum + (b+1)*(s+1)*lens.value
// }, sum, box...)
// }, 0, lis[:]...)
var sum int
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for b := range lis {
for s := range lis[b] {
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sum += (b + 1) * (s + 1) * lis[b][s].value
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}
}
return sum
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}