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package main | |
import ( | |
"fmt" | |
"io" | |
"log" | |
"os" | |
) | |
type image struct { | |
width, height int | |
layers [][]byte | |
} | |
func readImage(path string, width, height int) image { | |
f, err := os.Open(path) | |
if err != nil { | |
log.Fatal(err) | |
} | |
defer f.Close() | |
img := image{width, height, [][]byte{{}}} | |
b := make([]byte, 1) | |
for { | |
n, err := f.Read(b) | |
if n == 1 && b[0] != '\n' { | |
if len(img.layers[len(img.layers)-1]) == width*height { | |
img.layers = append(img.layers, []byte{}) | |
} | |
i := len(img.layers) - 1 | |
img.layers[i] = append(img.layers[i], b[0]-'0') | |
} else if err == io.EOF { | |
break | |
} else if err != nil { | |
log.Fatal(err) | |
} | |
} | |
return img | |
} | |
func zeroes(pixels []byte) int { | |
n := 0 | |
for _, p := range pixels { | |
if p == 0 { | |
n++ | |
} | |
} | |
return n | |
} | |
func layerChecksum(pixels []byte) int { | |
ones, twos := 0, 0 | |
for _, p := range pixels { | |
switch p { | |
case 1: | |
ones++ | |
case 2: | |
twos++ | |
} | |
} | |
return ones * twos | |
} | |
func checksum(img image) int { | |
fewestLayer := img.layers[0] | |
fewestZeroes := zeroes(fewestLayer) | |
x := layerChecksum(fewestLayer) | |
for _, layer := range img.layers[1:] { | |
if z := zeroes(layer); z < fewestZeroes { | |
fewestZeroes = z | |
fewestLayer = layer | |
x = layerChecksum(layer) | |
} | |
} | |
return x | |
} | |
func apply(base, layer []byte) { | |
for i := 0; i < len(base); i++ { | |
if layerPix := layer[i]; layerPix != 2 { | |
base[i] = layerPix | |
} | |
} | |
} | |
func decode(img image) []byte { | |
b := make([]byte, img.width*img.height) | |
for i := len(img.layers) - 1; i >= 0; i-- { | |
apply(b, img.layers[i]) | |
} | |
return b | |
} | |
func printImage(b []byte, width, height int) { | |
for i := 0; i < height; i++ { | |
for j := 0; j < width; j++ { | |
pix := b[i*width+j] | |
if pix == 0 { | |
fmt.Printf(" ") | |
} else { | |
fmt.Printf("%d", b[i*width+j]) | |
} | |
} | |
fmt.Println() | |
} | |
} | |
func main() { | |
img := readImage(os.Args[1], 25, 6) | |
fmt.Println(checksum(img)) | |
printImage(decode(img), 25, 6) | |
} |