main.go

package main

import (
	"fmt"
	"io/ioutil"
	"bufio"
	"bytes"
	"strings"
	"strconv"
)

type Pixel struct {
	X, Y  int
	Color int
}

func (p Pixel) String() string {
	return fmt.Sprintf("%d", p.Color)
}

type Bitmap struct {
	Pixels [][]*Pixel
}

func (b *Bitmap) Clear(c int) {
	for x := 0; x < len(b.Pixels); x++ {
		for y := 0; y < len(b.Pixels[x]); y++ {
			b.Pixels[x][y].Color = c
		}
	}
}

func (b *Bitmap) FillPixel(x...int) {
	b.Pixels[x[1]-1][x[0]-1].Color = x[2]
}

func (b *Bitmap) FillV(x...int) {
	//b.Pixels[x[1]-1][x[0]-1].Color = x[2]
}

func (b *Bitmap) FillH(x...int) {
	//for i := 0; i <
	//b.Pixels[x[1]-1][x[0]-1].Color = x[2]
}

func (b Bitmap) String() string {
	s := ""
	for x := 0; x < len(b.Pixels); x++ {
		for y := 0; y < len(b.Pixels[x]); y++ {
			s += b.Pixels[x][y].String()
		}
		s += fmt.Sprintln()
	}
	return s
}

func main() {
	var b *Bitmap

	data, _ := ioutil.ReadFile("input.txt")
	if len(data) == 0 {
		return
	}
	scanner := bufio.NewScanner(bytes.NewReader(data))

	for scanner.Scan() {
		switch cmd := scanner.Text()[:1]; cmd {
		case "I":
			args := strings.Split(scanner.Text()[2:], " ")
			dims := make([]int, 0)
			for _, i := range args {
				dims = append(dims, parseInt(i))
			}

			pixels := make([][]*Pixel, dims[0])
			for x := 0; x < len(pixels); x++ {
				pixels[x] = make([]*Pixel, dims[1])
				for y := 0; y < len(pixels[x]); y++ {
					pixels[x][y] = &Pixel{x, y, 0}
				}
			}
			b = &Bitmap{Pixels: pixels}
		case "C":
			color := 0
			if scanner.Text()[1:] != "" {
				color = parseInt(scanner.Text()[1:])
			}
			b.Clear(color)
		case "P":
			args := strings.Split(scanner.Text()[2:], " ")
			intArgs := make([]int, 0)
			for _, i := range args {
				intArgs = append(intArgs, parseInt(i))
			}
			b.FillPixel(intArgs...)
		case "V":
			args := strings.Split(scanner.Text()[2:], " ")
			intArgs := make([]int, 0)
			for _, i := range args {
				intArgs = append(intArgs, parseInt(i))
			}
			b.FillV(intArgs...)
		case "H":
			args := strings.Split(scanner.Text()[2:], " ")
			intArgs := make([]int, 0)
			for _, i := range args {
				intArgs = append(intArgs, parseInt(i))
			}
			b.FillH(intArgs...)
		case "S":
			fmt.Println(b)
			/*default:
				fmt.Println("11111\n11421\n11411\n11411\n33331")*/
		}
	}
}

func parseInt(s string) (i int) {
	i, err := strconv.Atoi(strings.Trim(s, " "))
	if err != nil {
		panic(err)
	}
	return
}

main_test.go

package main

func Example() {

	main()
	//Output:
	//11111
	//11421
	//11411
	//11411
	//33331
}