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main.go
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main.go
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package main
import (
"bufio"
"fmt"
"log"
"os"
"sort"
"strconv"
"strings"
)
type file struct {
name string
size int
}
type dir struct {
name string
parent *dir
dirs map[string]*dir
files []file
size int
}
func load() []string {
file, err := os.Open("input.txt")
if err != nil {
log.Fatalf("couldn't open file: %v", err)
}
defer file.Close()
vals := []string{}
scanner := bufio.NewScanner(file)
for scanner.Scan() {
val := scanner.Text()
vals = append(vals, val)
}
return vals
}
func update(v string, d *dir) {
vv := strings.Split(v, " ")
if len(vv) != 2 {
log.Fatalf("expected string to have 2 parts: %s", v)
}
if vv[0] == "dir" {
d.dirs[vv[1]] = &dir{
name: vv[1],
parent: d,
dirs: map[string]*dir{},
files: []file{},
}
} else {
size, err := strconv.Atoi(vv[0])
if err != nil {
log.Fatalf("expected string to start with size: %s", v)
}
d.files = append(d.files, file{
name: vv[1],
size: size,
})
}
}
func doCommand(v string, d *dir) *dir {
vv := strings.Split(v, " ")
if len(vv) < 2 {
log.Fatalf("expected string to have at least 2 parts: %s", v)
}
if vv[1] == "ls" {
return d
}
if vv[1] != "cd" || len(vv) != 3 {
log.Fatalf("did not get expected `cd` command: %s", v)
}
if vv[2] == ".." {
return d.parent
}
return d.dirs[vv[2]]
}
func next(v string, d *dir) *dir {
if v[0] == '$' {
d = doCommand(v, d)
} else {
update(v, d)
}
return d
}
func printDir(d *dir, dent string) {
fmt.Println(dent, d.name)
for _, dd := range d.dirs {
printDir(dd, dent+" ")
}
for _, f := range d.files {
fmt.Println(dent+" ", f.name, f.size)
}
}
func (d *dir) getSize() int {
if d.size == 0 {
for _, f := range d.files {
d.size += f.size
}
for _, dd := range d.dirs {
d.size += dd.getSize()
}
}
return d.size
}
func doSizes(dirs map[string]*dir, threshold int) int {
sum := 0
for _, d := range dirs {
size := d.getSize()
if size <= threshold {
sum += size
}
sum += doSizes(d.dirs, threshold)
}
return sum
}
func getDirs(d *dir) []*dir {
dirs := []*dir{d}
for _, dd := range d.dirs {
dirs = append(dirs, getDirs(dd)...)
}
return dirs
}
func main() {
vals := load()
root := &dir{
name: "/",
dirs: map[string]*dir{},
files: []file{},
}
d := root
for _, v := range vals[1:] {
d = next(v, d)
}
// printDir(root, "")
size := doSizes(root.dirs, 100000)
fmt.Println(size)
totalSize := 70000000
need := 30000000
spaceNeeded := need - (totalSize - root.getSize())
dirs := getDirs(root)
sort.SliceStable(dirs, func(i, j int) bool {
return dirs[i].size > dirs[j].size
})
smallest := dirs[0].size
for _, d := range dirs {
if d.size >= spaceNeeded && d.size < smallest {
fmt.Println("candidate", d.name, d.size)
smallest = d.size
}
}
fmt.Println(smallest)
}