93 lines
1.9 KiB
Go
93 lines
1.9 KiB
Go
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package main
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import (
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"fmt"
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"os"
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"strings"
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"github.com/kelindar/bitmap"
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)
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func readLines(filename string) []string {
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raw, err := os.ReadFile(filename)
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if err != nil {
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panic(err)
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}
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return strings.Split(string(raw), "\n")
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}
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type warehouse struct {
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boxes bitmap.Bitmap
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width uint32
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height uint32
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}
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func buildWarehouse(lines []string) warehouse {
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wh := warehouse{}
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wh.height = uint32(len(lines))
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if wh.height == 0 {
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return wh
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}
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wh.width = uint32(len(lines[0]))
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if wh.width == 0 {
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return wh
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}
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for y, line := range lines {
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for x, char := range line {
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if char == '@' {
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set(&wh.boxes, wh.width, wh.height, uint32(x), uint32(y))
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}
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}
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}
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return wh
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}
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func set(area *bitmap.Bitmap, width uint32, height uint32, x uint32, y uint32) {
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if x >= width || y >= height {
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return
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}
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area.Set(y*width + x)
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}
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func debug(area *bitmap.Bitmap, width uint32) {
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area.Range(func(offset uint32) {
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fmt.Printf("(%d, %d)\n", offset%width, offset/width)
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})
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}
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func buildNeighbors(width uint32, height uint32, x uint32, y uint32) *bitmap.Bitmap {
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var neighbors bitmap.Bitmap
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set(&neighbors, width, height, x+1, y)
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set(&neighbors, width, height, x-1, y)
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set(&neighbors, width, height, x+1, y+1)
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set(&neighbors, width, height, x-1, y+1)
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set(&neighbors, width, height, x+1, y-1)
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set(&neighbors, width, height, x-1, y-1)
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set(&neighbors, width, height, x, y+1)
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set(&neighbors, width, height, x, y-1)
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return &neighbors
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}
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func (wh warehouse) countAccessibleBoxes() uint32 {
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boxes := wh.boxes.Clone(nil)
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boxes.Filter(func(offset uint32) bool {
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y := offset / wh.width
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x := offset % wh.width
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neighbors := buildNeighbors(wh.width, wh.height, x, y)
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neighbors.And(wh.boxes)
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accessible := neighbors.Count() < 4
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return accessible
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})
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return uint32(boxes.Count())
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}
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func main() {
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filename := "input0.txt"
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if len(os.Args) > 1 {
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filename = os.Args[1]
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}
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lines := readLines(filename)
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wh := buildWarehouse(lines)
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fmt.Printf("%v\n", wh.countAccessibleBoxes())
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}
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