task: Day 13: Claw Contraption

Author: Norbiros

day_13/main.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	_ "embed"
+	"fmt"
+	"github.com/Norbiros/AoC2024/utils"
+	"gonum.org/v1/gonum/mat"
+	"math"
+	"strings"
+)
+
+//go:embed input.txt
+var input string
+
+// I know this solution isn't bulletproof
+// It won't work, for example, for buttons [1, 1] = 2 [5, 5] = 10
+// But it worked for my dataset :3
+func main() {
+	fmt.Println("Solving \"Day 13: Claw Contraption\"...")
+	fmt.Println("Part 1 result", solve(input, 0))
+	fmt.Println("Part 2 result", solve(input, 10000000000000))
+}
+
+func parseCoordinates(line, prefix string) []int {
+	line = strings.ReplaceAll(line, prefix, "")
+	line = strings.ReplaceAll(line, ", Y", " ")
+	line = strings.ReplaceAll(line, "=", "")
+	values := strings.Fields(line)
+	return []int{utils.ToInt(values[0]), utils.ToInt(values[1])}
+}
+
+func solve(input string, difference int) int {
+	var resultValue int
+	for _, line := range strings.Split(input, "\n\n") {
+		lines := strings.Split(line, "\n")
+		buttonA := parseCoordinates(lines[0], "Button A: X")
+		buttonB := parseCoordinates(lines[1], "Button B: X")
+
+		prize := parseCoordinates(lines[2], "Prize: X")
+		prize[0] += difference
+		prize[1] += difference
+
+		matrix := mat.NewDense(2, 2, []float64{
+			float64(buttonA[0]), float64(buttonB[0]),
+			float64(buttonA[1]), float64(buttonB[1]),
+		})
+		result := mat.NewDense(2, 1, []float64{
+			float64(prize[0]),
+			float64(prize[1]),
+		})
+
+		var solution mat.Dense
+		err := solution.Solve(matrix, result)
+		if err != nil {
+			fmt.Println("Error solving equations:", err)
+			continue
+		}
+
+		a, b := solution.At(0, 0), solution.At(1, 0)
+
+		const epsilon = 1e-4
+		if math.Abs(a-math.Round(a)) < epsilon && math.Abs(b-math.Round(b)) < epsilon {
+			resultValue += int(math.Round(a)*3 + math.Round(b))
+		}
+
+	}
+	return resultValue
+}