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day05.go
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day05.go
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package main
import (
"bytes"
"io"
"github.com/armsnyder/aoc2022/aocutil"
"github.com/samber/lo"
)
var _ = declareDay(5, func(part2 bool, inputReader io.Reader) any {
if part2 {
return day05Part2(inputReader)
}
return day05Part1(inputReader)
})
func day05Part1(inputReader io.Reader) any {
return day05UsingCrane(inputReader, func(stacks *day05Stacks, n, from, to int) {
for i := 0; i < n; i++ {
(*stacks)[to] = append((*stacks)[to], (*stacks)[from][len((*stacks)[from])-1])
(*stacks)[from] = (*stacks)[from][:len((*stacks)[from])-1]
}
})
}
func day05Part2(inputReader io.Reader) any {
return day05UsingCrane(inputReader, func(stacks *day05Stacks, n, from, to int) {
(*stacks)[to] = append((*stacks)[to], (*stacks)[from][len((*stacks)[from])-n:]...)
(*stacks)[from] = (*stacks)[from][:len((*stacks)[from])-n]
})
}
type day05Stacks [9][]byte
func day05UsingCrane(inputReader io.Reader, crane func(stacks *day05Stacks, n, from, to int)) string {
var stacks day05Stacks
scanningCrates := true
aocutil.VisitStrings(inputReader, func(v []byte) {
if v[1] > '0' && v[1] <= '9' {
scanningCrates = false
for i := range stacks {
lo.Reverse(stacks[i])
}
return
}
if scanningCrates {
for crateIndex := 1; crateIndex < len(v); crateIndex += 4 {
stackIndex := crateIndex / 4
if v[crateIndex] != ' ' {
stacks[stackIndex] = append(stacks[stackIndex], v[crateIndex])
}
}
return
}
split := bytes.SplitN(v, []byte{' '}, 6)
n, _ := aocutil.AtoiBytes(split[1])
from, _ := aocutil.AtoiBytes(split[3])
from -= 1
to, _ := aocutil.AtoiBytes(split[5])
to -= 1
crane(&stacks, n, from, to)
})
result := make([]byte, 0, len(stacks))
for _, stack := range stacks {
if len(stack) == 0 {
break
}
result = append(result, stack[len(stack)-1])
}
return string(result)
}