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day07.go
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day07.go
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package main
import (
"bytes"
"io"
"sort"
"github.com/armsnyder/aoc2022/aocutil"
"github.com/samber/lo"
)
var _ = declareDay(7, func(part2 bool, inputReader io.Reader) any {
if part2 {
return day07Part2(inputReader)
}
return day07Part1(inputReader)
})
func day07Part1(inputReader io.Reader) any {
root := day07BuildFileSystem(inputReader)
total := 0
var visit func(node *day07File) int
visit = func(node *day07File) int {
if len(node.children) == 0 {
return node.size
}
size := 0
for _, child := range node.children {
size += visit(child)
}
if size <= 100000 {
total += size
}
return size
}
visit(root)
return total
}
func day07Part2(inputReader io.Reader) any {
root := day07BuildFileSystem(inputReader)
var sortedDirSizes []int
var visit func(node *day07File) int
visit = func(node *day07File) int {
if len(node.children) == 0 {
return node.size
}
size := 0
for _, child := range node.children {
size += visit(child)
}
insertIndex := sort.SearchInts(sortedDirSizes, size)
sortedDirSizes = append(sortedDirSizes, 0)
copy(sortedDirSizes[insertIndex+1:], sortedDirSizes[insertIndex:])
sortedDirSizes[insertIndex] = size
return size
}
const diskSize = 70000000
const needUnusedSpace = 30000000
fileSystemSize := visit(root)
needDeleted := needUnusedSpace - (diskSize - fileSystemSize)
minSizeIndex := sort.SearchInts(sortedDirSizes, needDeleted)
return sortedDirSizes[minSizeIndex]
}
type day07File struct {
size int
name string
parent *day07File
children []*day07File
}
func day07BuildFileSystem(inputReader io.Reader) *day07File {
root := &day07File{name: "/"}
var cur *day07File
aocutil.VisitStrings(inputReader, func(v []byte) {
if v[0] == '$' {
if string(v[2:4]) != "cd" {
return
}
cdDir := string(v[bytes.LastIndexByte(v, ' ')+1:])
switch cdDir {
case "/":
cur = root
case "..":
cur = cur.parent
default:
cur, _ = lo.Find(cur.children, func(child *day07File) bool {
return child.name == cdDir
})
}
return
}
spaceIndex := bytes.IndexByte(v, ' ')
name := string(v[spaceIndex+1:])
if !lo.ContainsBy(cur.children, func(node *day07File) bool {
return node.name == name
}) {
newNode := &day07File{
name: name,
parent: cur,
}
if string(v[:spaceIndex]) != "dir" {
newNode.size, _ = aocutil.AtoiBytes(v[:spaceIndex])
}
cur.children = append(cur.children, newNode)
}
})
return root
}