124 lines
1.9 KiB
Go
124 lines
1.9 KiB
Go
package main
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import (
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"fmt"
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"strings"
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"github.com/jdkaplan/advent-of-code/aoc"
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)
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func main() {
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text := aoc.Input().ReadFile("day13.txt")
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fmt.Println(part1(text))
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fmt.Println(part2(text))
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}
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func part1(text string) int {
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g, folds := parse(text)
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g = g.Fold(folds[0])
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return len(g)
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}
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func part2(text string) string {
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g, folds := parse(text)
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for _, f := range folds {
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g = g.Fold(f)
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}
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return g.String()
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}
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func parse(text string) (Grid, []Fold) {
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dots, folds := aoc.Cut(text, "\n\n")
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var points []Point
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for _, line := range strings.Split(dots, "\n") {
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x, y := aoc.Cut(line, ",")
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points = append(points, Point{
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x: aoc.MustInt(x),
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y: aoc.MustInt(y),
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})
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}
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var fs []Fold
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for _, line := range strings.Split(folds, "\n") {
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axis, val := aoc.Cut(line[len("fold along "):], "=")
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fs = append(fs, Fold{
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axis: axis,
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val: aoc.MustInt(val),
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})
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}
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return NewGrid(points), fs
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}
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type Point struct{ x, y int }
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type Grid map[Point]int
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type Fold struct {
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axis string
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val int
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}
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func NewGrid(points []Point) Grid {
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g := make(Grid)
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for _, p := range points {
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g[p] = 1
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}
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return g
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}
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func (g Grid) Fold(f Fold) Grid {
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g2 := make(Grid)
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for p, count := range g {
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var p2 Point
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switch axis := f.axis; axis {
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case "x":
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p2 = p.foldX(f.val)
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case "y":
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p2 = p.foldY(f.val)
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default:
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panic(axis)
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}
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g2[p2] += count
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}
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return g2
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}
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func (p Point) foldX(x int) Point {
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if p.x > x {
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return Point{x - (p.x - x), p.y}
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}
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return p
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}
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func (p Point) foldY(y int) Point {
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if p.y > y {
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return Point{p.x, y - (p.y - y)}
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}
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return p
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}
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func (g Grid) String() string {
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xmax, ymax := 0, 0
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for p := range g {
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if p.x > xmax {
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xmax = p.x
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}
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if p.y > ymax {
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ymax = p.y
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}
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}
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var sb strings.Builder
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for y := 0; y <= ymax; y++ {
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for x := 0; x <= xmax; x++ {
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_, ok := g[Point{x, y}]
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if ok {
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sb.WriteString("█")
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} else {
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sb.WriteString(" ")
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}
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}
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sb.WriteString("\n")
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}
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return sb.String()
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}
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