Add solution for day 6 part 1

Author: terminalnode

README.md

@@ -50,7 +50,7 @@ automatically rebuilt and redeployed ever time the `common` module or their own
 | 03  | ⭐ ⭐      | 16  |          |
 | 04  | ⭐ ⭐      | 17  |          |
 | 05  | ⭐ ⭐      | 18  |          |
-| 06  |          | 19  |          |
+| 06  | ⭐        | 19  |          |
 | 07  |          | 20  |          |
 | 08  |          | 21  |          |
 | 09  |          | 22  |          |

solutions/day06/main.go

@@ -1,9 +1,130 @@
 package main
 
 import (
+	"errors"
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
+	"github.com/terminalnode/adventofcode2024/common/util"
+	"strings"
 )
 
+// Due to function types not implementing == or !=, I need to store the direction as an int.
+
+type Coordinate = util.Coordinate
+type BoolMatrix = util.BoolMatrix
+type direction = int
+
+var directions = []util.Direction{
+	Coordinate.North,
+	Coordinate.East,
+	Coordinate.South,
+	Coordinate.West,
+}
+
+type parsedInput struct {
+	Guard       Coordinate
+	Direction   direction
+	ObstacleMap BoolMatrix
+	VisitedMap  BoolMatrix
+}
+
 func main() {
-	common.Setup(6, nil, nil)
+	common.Setup(6, part1, nil)
+}
+
+func part1(
+	input string,
+) string {
+	parsed, err := parseInput(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse input: %v", err)
+	}
+
+	for parsed.move() {
+		// Do nothing, move() does all the work
+	}
+	count := util.CountInMatrix(parsed.VisitedMap, true)
+	return fmt.Sprintf("Visited spots in the Matrix: %d", count)
+}
+
+func parseInput(
+	input string,
+) (parsedInput, error) {
+	var guard Coordinate
+	var obstacles BoolMatrix
+	var visited BoolMatrix
+	var err error
+
+	lines := strings.Split(input, "\n")
+	maxY := len(lines) - 1
+	maxX := len(lines[0]) - 1
+
+	rawObstacles := make([][]bool, maxY+1)
+	rawVisited := make([][]bool, maxY+1)
+
+	foundGuard := false
+	for y := 0; y <= maxY; y++ {
+		rawObstacles[y] = make([]bool, maxX+1)
+		rawVisited[y] = make([]bool, maxX+1)
+
+		for x := 0; x <= maxX; x++ {
+			c := lines[y][x]
+			rawObstacles[y][x] = c == '#'
+			if c == '^' {
+				foundGuard = true
+				guard = Coordinate{X: x, Y: y}
+				rawVisited[y][x] = true
+			}
+		}
+	}
+	if foundGuard == false {
+		return parsedInput{}, errors.New("could not find guard in matrix")
+	}
+
+	obstacles, err = util.NewMatrixFromRows(rawObstacles)
+	if err != nil {
+		return parsedInput{}, fmt.Errorf("failed to create obstacle matrix: %v", err)
+	}
+
+	visited, err = util.NewMatrixFromRows(rawVisited)
+	if err != nil {
+		return parsedInput{}, fmt.Errorf("failed to create visited matrix: %v", err)
+	}
+
+	return parsedInput{
+		Guard:       guard,
+		Direction:   0, // This means north
+		ObstacleMap: obstacles,
+		VisitedMap:  visited,
+	}, nil
+}
+
+// Move and return a boolean indicating whether the guard is inside the matrix or not
+func (
+	p *parsedInput,
+) move() bool {
+	newPos := getNewPosition(p.Guard, p.Direction)
+	isBlocked, err := p.ObstacleMap.Get(newPos.X, newPos.Y)
+	if err != nil {
+		return false
+	} else if isBlocked {
+		p.rotate()
+		newPos = getNewPosition(p.Guard, p.Direction)
+	}
+	p.Guard = newPos
+
+	err = p.VisitedMap.Set(p.Guard.X, p.Guard.Y, true)
+	return err == nil
+}
+
+func (p *parsedInput) rotate() {
+	p.Direction = (p.Direction + 1) % 4
+}
+
+func getNewPosition(
+	guard Coordinate,
+	direction int,
+) Coordinate {
+	dirF := directions[direction]
+	return dirF(guard)
 }