Add solution day 14 part 1

Author: terminalnode

README.md

@@ -45,7 +45,7 @@ automatically rebuilt and redeployed ever time the `common` module or their own
 
 | Day | Solution | Day | Solution |
 |-----|----------|-----|----------|
-| 01  | ⭐ ⭐      | 14  |          |
+| 01  | ⭐ ⭐      | 14  | ⭐        |
 | 02  | ⭐ ⭐      | 15  |          |
 | 03  | ⭐ ⭐      | 16  |          |
 | 04  | ⭐ ⭐      | 17  |          |

common/util/coordinate.go

@@ -19,6 +19,34 @@ func In2DArray[T any](
 	return !invalid
 }
 
+func (c Coordinate) Add(x int, y int) Coordinate {
+	return Coordinate{X: c.X + x, Y: c.Y + y}
+}
+
+func (c Coordinate) Multiply(x int, y int) Coordinate {
+	return Coordinate{X: c.X * x, Y: c.Y * y}
+}
+
+func (c Coordinate) Modulo(x int, y int) Coordinate {
+	return Coordinate{X: c.X % x, Y: c.Y % y}
+}
+
+func (c Coordinate) PositiveModulo(x int, y int) Coordinate {
+	// This is similar to how modulo works in Python
+	// See: https://stackoverflow.com/questions/13794171/how-to-make-the-mod-of-a-negative-number-to-be-positive/13794192
+
+	if x < 0 {
+		x = -x
+	}
+	if y < 0 {
+		y = -y
+	}
+	return Coordinate{
+		X: ((c.X % x) + x) % x,
+		Y: ((c.Y % y) + y) % y,
+	}
+}
+
 func (c Coordinate) North() Coordinate {
 	return Coordinate{c.X, c.Y - 1}
 }

solutions/day14/main.go

@@ -1,9 +1,55 @@
 package main
 
 import (
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
 )
 
 func main() {
-	common.Setup(14, nil, nil)
+	common.Setup(14, part1, nil)
+}
+
+func part1(
+	input string,
+) string {
+	return solve(input, 100, 100, 102)
+}
+
+func solve(
+	input string,
+	seconds int,
+	maxX int,
+	maxY int,
+) string {
+	// Lines assume that the board is an uneven number of tiles
+	horizontalLine := maxY / 2
+	verticalLine := maxX / 2
+
+	robots, err := parseRobots(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse robots: %v", err)
+	}
+
+	q1, q2, q3, q4 := 0, 0, 0, 0
+	for _, r := range robots {
+		move := r.move.Multiply(seconds, seconds)
+		newPos := r.init.Add(move.X, move.Y).PositiveModulo(maxX+1, maxY+1)
+
+		if newPos.X < verticalLine {
+			if newPos.Y < horizontalLine {
+				q1++
+			} else if newPos.Y > horizontalLine {
+				q2++
+			}
+		} else if newPos.X > verticalLine {
+			if newPos.Y < horizontalLine {
+				q3++
+			} else if newPos.Y > horizontalLine {
+				q4++
+			}
+		}
+	}
+
+	safetyFactor := q1 * q2 * q3 * q4
+	return fmt.Sprintf("After 100 seconds, area has a safety factor of %d", safetyFactor)
 }

solutions/day14/parse.go

@@ -0,0 +1,59 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"github.com/terminalnode/adventofcode2024/common/util"
+	"regexp"
+	"strconv"
+)
+
+type robot struct {
+	init util.Coordinate
+	move util.Coordinate
+}
+
+func (r robot) String() string {
+	return fmt.Sprintf(
+		"p=%d,%d v=%d,%d",
+		r.init.X,
+		r.init.Y,
+		r.move.X,
+		r.move.Y,
+	)
+}
+
+var rx = regexp.MustCompile(`p=(-?\d+),(-?\d+) v=(-?\d+),(-?\d+)`)
+
+func parseRobots(
+	input string,
+) ([]robot, error) {
+	matches := rx.FindAllSubmatch([]byte(input), -1)
+	robots := make([]robot, len(matches))
+
+	if len(robots) == 0 {
+		return robots, errors.New("input set contains no robots")
+	}
+
+	for i, match := range matches {
+		if len(match) != 5 {
+			return robots, fmt.Errorf("expected match to be 5 long, but was %d", len(match))
+		}
+
+		numbers := make([]int, 4)
+		for j := 0; j < 4; j++ {
+			n, err := strconv.ParseInt(string(match[j+1]), 10, 0)
+			if err != nil {
+				return robots, err
+			}
+			numbers[j] = int(n)
+		}
+
+		robots[i] = robot{
+			init: util.Coordinate{X: numbers[0], Y: numbers[1]},
+			move: util.Coordinate{X: numbers[2], Y: numbers[3]},
+		}
+	}
+
+	return robots, nil
+}