Add solution day 13 part 1

Author: terminalnode

Dockerfile

@@ -14,7 +14,7 @@ COPY common common
 
 ARG DAY
 COPY solutions/day${DAY} solutions/day${DAY}
-RUN go build -o app solutions/day${DAY}/main.go
+RUN go build -o app solutions/day${DAY}/*
 EXPOSE 3000
 
 HEALTHCHECK \

README.md

@@ -57,4 +57,4 @@ automatically rebuilt and redeployed ever time the `common` module or their own
 | 10  | ⭐ ⭐      | 23  |          |
 | 11  | ⭐ ⭐      | 24  |          |
 | 12  | ⭐ ⭐      | 25  |          |
-| 13  |          |     |          |
+| 13  | ⭐        |     |          |

solutions/day13/main.go

@@ -1,9 +1,80 @@
 package main
 
 import (
+	"fmt"
 	"github.com/terminalnode/adventofcode2024/common"
+	"github.com/terminalnode/adventofcode2024/common/util"
+	"log"
+	"math"
 )
 
 func main() {
-	common.Setup(13, nil, nil)
+	common.Setup(13, part1, nil)
+}
+
+func part1(
+	input string,
+) string {
+	problems, err := parseProblems(input)
+	if err != nil {
+		return fmt.Sprintf("Failed to parse input: %v", err)
+	}
+
+	sum := 0
+	for _, p := range problems {
+		minTokenCost := findMinTokenCost(p)
+		if minTokenCost != -1 {
+			sum += minTokenCost
+		}
+	}
+
+	return fmt.Sprintf("At least %d tokens to solve these %d claw machines", sum, len(problems))
+}
+
+func findMinTokenCost(
+	p problem,
+) int {
+	smallest := math.MaxInt
+
+	for timesA := 0; true; timesA++ {
+		c := util.Coordinate{
+			X: timesA * p.a.X,
+			Y: timesA * p.a.Y,
+		}
+		if c.X > p.goal.X || c.Y > p.goal.Y {
+			break
+		}
+
+		minMoves := findMinTokenCostAfterA(c, timesA, p)
+		if minMoves != -1 && minMoves < smallest {
+			log.Printf("New smallest! %d", minMoves)
+			smallest = minMoves
+		}
+	}
+
+	if smallest == math.MaxInt {
+		return -1
+	}
+	return smallest
+}
+
+func findMinTokenCostAfterA(
+	c util.Coordinate,
+	timesA int,
+	p problem,
+) int {
+	for timesB := 0; true; timesB++ {
+		newC := util.Coordinate{
+			X: timesB*p.b.X + c.X,
+			Y: timesB*p.b.Y + c.Y,
+		}
+
+		if newC.X > p.goal.X || newC.Y > p.goal.Y {
+			break
+		} else if newC.X == p.goal.X && newC.Y == p.goal.Y {
+			return timesA*3 + timesB
+		}
+	}
+
+	return -1
 }

solutions/day13/parse.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"github.com/terminalnode/adventofcode2024/common/util"
+	"regexp"
+	"strconv"
+)
+
+type problem struct {
+	a    util.Coordinate
+	b    util.Coordinate
+	goal util.Coordinate
+}
+
+var r = regexp.MustCompile(`Button A: X\+(\d+), Y\+(\d+)\nButton B: X\+(\d+), Y\+(\d+)\nPrize: X=(\d+), Y=(\d+)`)
+
+func parseProblems(
+	input string,
+) ([]problem, error) {
+	matches := r.FindAllSubmatch([]byte(input), -1)
+	problems := make([]problem, len(matches))
+
+	if len(problems) == 0 {
+		return problems, errors.New("input set contains no problems")
+	}
+
+	for i, match := range matches {
+		if len(match) < 7 {
+			return problems, fmt.Errorf("expected match to be at least 7 long, but was %d", len(match))
+		}
+
+		digits := make([]int, 6)
+		for j := 0; j < 6; j++ {
+			d, err := strconv.ParseInt(string(match[j+1]), 10, 0)
+			if err != nil {
+				return problems, err
+			}
+			digits[j] = int(d)
+		}
+
+		problems[i] = problem{
+			a:    util.Coordinate{X: digits[0], Y: digits[1]},
+			b:    util.Coordinate{X: digits[2], Y: digits[3]},
+			goal: util.Coordinate{X: digits[4], Y: digits[5]},
+		}
+	}
+
+	return problems, nil
+}