Day13

2024/gareth/day13/day13.go

@@ -0,0 +1,76 @@
+package day13
+
+import (
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+type ClawMachine struct {
+	Ax, Ay int
+	Bx, By int
+	Px, Py int
+}
+
+func Part1(input string) int {
+	clawMachines := parseInput(input)
+	total := 0
+	for _, c := range clawMachines {
+		x, y := solveSimEquations(c.Ax, c.Bx, c.Px, c.Ay, c.By, c.Py)
+		total += x*3 + y
+	}
+	return total
+}
+
+func Part2(input string) int {
+	clawMachines := parseInput(input)
+	total := 0
+	for _, c := range clawMachines {
+		prizeX, prizeY := c.Px+10000000000000, c.Py+10000000000000
+		det, x, y := c.Ax*c.By-c.Bx*c.Ay, prizeX*c.By-c.Bx*prizeY, c.Ax*prizeY-prizeX*c.Ay
+		if det != 0 && x == (x/det)*det && y == (y/det)*det {
+			total += (x/det)*3 + (y / det)
+		}
+	}
+
+	return total
+}
+
+func parseInput(input string) []ClawMachine {
+	clawMachines := strings.Split(strings.TrimSpace(input), "\n\n")
+	output := make([]ClawMachine, 0, len(clawMachines))
+	for _, c := range clawMachines {
+		var clawMachine ClawMachine
+		line := strings.Split(strings.TrimSpace(c), "\n")
+
+		re := regexp.MustCompile(`X\+(\d+), Y\+(\d+)`)
+		matches := re.FindStringSubmatch(line[0])
+		clawMachine.Ax, _ = strconv.Atoi(matches[1])
+		clawMachine.Ay, _ = strconv.Atoi(matches[2])
+
+		matches = re.FindStringSubmatch(line[1])
+		clawMachine.Bx, _ = strconv.Atoi(matches[1])
+		clawMachine.By, _ = strconv.Atoi(matches[2])
+
+		re = regexp.MustCompile(`X=(\d+), Y=(\d+)`)
+		matches = re.FindStringSubmatch(line[2])
+		clawMachine.Px, _ = strconv.Atoi(matches[1])
+		clawMachine.Py, _ = strconv.Atoi(matches[2])
+
+		output = append(output, clawMachine)
+	}
+	return output
+}
+
+func solveSimEquations(a1, b1, c1, a2, b2, c2 int) (int, int) {
+	det := a1*b2 - a2*b1
+	if det == 0 || (c1*b2-c2*b1)%det != 0 || (a1*c2-a2*c1)%det != 0 {
+		return 0, 0
+	}
+	x := (c1*b2 - c2*b1) / det
+	y := (a1*c2 - a2*c1) / det
+	if x < 0 || x > 100 || y < 0 || y > 100 {
+		return 0, 0
+	}
+	return x, y
+}

2024/gareth/day13/day13_test.go

@@ -0,0 +1,45 @@
+package day13
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+	r := Part1(`Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279`)
+	assert.Equal(t, 480, r)
+}
+
+func TestPart2(t *testing.T) {
+	r := Part2(`Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279`)
+	assert.Equal(t, 0, r)
+}

2024/gareth/main.go

@@ -1,7 +1,7 @@
 package main
 
 import (
-	"aoc2024/day11"
+	"aoc2024/day13"
 	"fmt"
 	"os"
 	"time"
@@ -9,9 +9,9 @@ import (
 
 func main() {
 	start := time.Now()
-	data, _ := os.ReadFile("day11/input.txt")
-	fmt.Printf("part 1: %d\n", day11.Part1(string(data)))
-	fmt.Printf("part 2: %d\n", day11.Part2(string(data)))
+	data, _ := os.ReadFile("day13/input.txt")
+	fmt.Printf("part 1: %d\n", day13.Part1(string(data)))
+	fmt.Printf("part 2: %d\n", day13.Part2(string(data)))
 	elapsed := time.Since(start)
 	fmt.Printf("Execution time: %s\n", elapsed)
 }