Add day 09

This was a hekkin hekker ...

Author: vimkat

09/example-2.txt

@@ -0,0 +1,8 @@
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20

09/example.txt

@@ -0,0 +1,8 @@
+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2

09/main.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/vimkat/aoc-2022/util"
+)
+
+func main() {
+	part1("example.txt")
+	part1("puzzle.txt")
+	fmt.Println()
+	part2("example.txt")
+	part2("example-2.txt")
+	part2("puzzle.txt")
+}
+
+func part1(path string) { simulateRope(path, 2) }
+func part2(path string) { simulateRope(path, 10) }
+
+func simulateRope(path string, ropeLength int) {
+	rope := NewRope(ropeLength)
+
+	for line := range util.ReadByLines(path) {
+		parsed := strings.Split(line, " ")
+		repeat := util.MustValue(strconv.Atoi(parsed[1]))
+
+		for i := 0; i < repeat; i++ {
+			switch parsed[0] {
+			case "L":
+				rope.Move(-1, 0)
+			case "R":
+				rope.Move(1, 0)
+			case "U":
+				rope.Move(0, -1)
+			case "D":
+				rope.Move(0, 1)
+			}
+		}
+
+		// Print steps
+		// if strings.HasPrefix(path, "example") {
+		// 	rope.PrettyPrint(35, 35, 15, 15)
+		// 	fmt.Println()
+		// }
+	}
+
+	fmt.Println(len(rope.Visited()))
+}

09/model.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/vimkat/aoc-2022/util"
+)
+
+type Pos struct{ x, y int }
+
+func (p Pos) String() string   { return fmt.Sprintf("(%d/%d)", p.x, p.y) }
+func (p Pos) Add(x, y int) Pos { return Pos{p.x + x, p.y + y} }
+
+func (p Pos) IsAdjacent(other Pos) bool {
+	return util.Abs(p.x-other.x) <= 1 && util.Abs(p.y-other.y) <= 1
+}
+
+func (p Pos) MakeAdjacentTo(other Pos) Pos {
+	if p.IsAdjacent(other) {
+		return p
+	}
+
+	if p.x == other.x {
+		return Pos{other.x, other.y - util.Sign(other.y-p.y)}
+	}
+
+	if p.y == other.y {
+		return Pos{other.x - util.Sign(other.x-p.x), other.y}
+	}
+
+	dx := util.Abs(other.x - p.x)
+	dy := util.Abs(other.y - p.y)
+
+	if dx < dy {
+		return Pos{other.x, other.y - util.Sign(other.y-p.y)}
+	}
+
+	if dy < dx {
+		return Pos{other.x - util.Sign(other.x-p.x), other.y}
+	}
+
+	return Pos{
+		other.x - util.Sign(other.x-p.x),
+		other.y - util.Sign(other.y-p.y),
+	}
+}
+
+type Rope struct {
+	rope    []Pos
+	visited map[Pos]int
+}
+
+func NewRope(ropeLength int) *Rope {
+	r := Rope{
+		rope:    make([]Pos, ropeLength),
+		visited: make(map[Pos]int),
+	}
+
+	// Start position has already been visited
+	r.visited[Pos{0, 0}] = 1
+
+	return &r
+}
+
+func (r *Rope) Move(dx, dy int) {
+	// Move the head
+	r.rope[0] = r.rope[0].Add(dx, dy)
+
+	// Update the tail(s)
+	for i := 1; i < len(r.rope); i++ {
+		r.rope[i] = r.rope[i].MakeAdjacentTo(r.rope[i-1])
+	}
+
+	// Mark visited
+	val := r.visited[r.rope[len(r.rope)-1]]
+	val += 1
+	r.visited[r.rope[len(r.rope)-1]] = val
+}
+
+func (r Rope) Visited() map[Pos]int {
+	return r.visited
+}
+
+func (r Rope) PrettyPrint(width, height, centerX, centerY int) {
+	grid := make([][]rune, height)
+	for row := 0; row < height; row++ {
+		grid[row] = make([]rune, width)
+		for col := 0; col < width; col++ {
+			grid[row][col] = '.'
+		}
+	}
+
+	grid[centerY][centerX] = 'S'
+
+	// Print knots
+	for i, knot := range r.rope {
+		grid[knot.y+centerY][knot.x+centerX] = rune(i + '0')
+	}
+
+	for row := 0; row < height; row++ {
+		fmt.Println(string(grid[row]))
+	}
+}