Day 15

d15/input.txt

@@ -0,0 +1,4 @@
+Sprinkles: capacity 2, durability 0, flavor -2, texture 0, calories 3
+Butterscotch: capacity 0, durability 5, flavor -3, texture 0, calories 3
+Chocolate: capacity 0, durability 0, flavor 5, texture -1, calories 8
+Candy: capacity 0, durability -1, flavor 0, texture 5, calories 8

d15/main.go

@@ -0,0 +1,124 @@
+package main
+
+import (
+	"aoc2015/util"
+	"regexp"
+	"slices"
+)
+
+type Ingredient struct {
+	Name       string
+	Capacity   int
+	Durability int
+	Flavor     int
+	Texture    int
+	Calories   int
+}
+
+func part1(ingredients []Ingredient) int {
+	ingredientsCount := len(ingredients)
+
+	combinations := util.CombinationsWithSum(ingredientsCount, 100)
+	sums := util.ArrayMap(combinations, func(combination []int) int {
+		capacity := 0
+		durability := 0
+		flavor := 0
+		texture := 0
+
+		for i := 0; i < ingredientsCount; i++ {
+			capacity += combination[i] * ingredients[i].Capacity
+			durability += combination[i] * ingredients[i].Durability
+			flavor += combination[i] * ingredients[i].Flavor
+			texture += combination[i] * ingredients[i].Texture
+		}
+
+		if capacity < 0 {
+			capacity = 0
+		}
+
+		if durability < 0 {
+			durability = 0
+		}
+
+		if flavor < 0 {
+			flavor = 0
+		}
+
+		if texture < 0 {
+			texture = 0
+		}
+
+		return capacity * durability * flavor * texture
+	})
+
+	return slices.Max(sums)
+}
+
+func part2(ingredients []Ingredient) int {
+	ingredientsCount := len(ingredients)
+
+	combinations := util.CombinationsWithSum(ingredientsCount, 100)
+	sums := util.ArrayMap(combinations, func(combination []int) int {
+		capacity := 0
+		durability := 0
+		flavor := 0
+		texture := 0
+		calories := 0
+
+		for i := 0; i < ingredientsCount; i++ {
+			capacity += combination[i] * ingredients[i].Capacity
+			durability += combination[i] * ingredients[i].Durability
+			flavor += combination[i] * ingredients[i].Flavor
+			texture += combination[i] * ingredients[i].Texture
+			calories += combination[i] * ingredients[i].Calories
+		}
+
+		if capacity < 0 {
+			capacity = 0
+		}
+
+		if durability < 0 {
+			durability = 0
+		}
+
+		if flavor < 0 {
+			flavor = 0
+		}
+
+		if texture < 0 {
+			texture = 0
+		}
+
+		if calories != 500 {
+			return 0
+		}
+
+		return capacity * durability * flavor * texture
+	})
+
+	return slices.Max(sums)
+}
+
+// Lol, it's basically a SAT solver
+func main() {
+	lineRegexp := regexp.MustCompile(`^(\w+): \w+ ([0-9-]+), \w+ ([0-9-]+), \w+ ([0-9-]+), \w+ ([0-9-]+), \w+ ([0-9-]+)$`)
+	reader := func(name string) []Ingredient {
+		lines := util.ReadLines(name)
+
+		return util.ArrayMap(lines, func(line string) Ingredient {
+			match := lineRegexp.FindStringSubmatch(line)
+
+			return Ingredient{
+				Name:       match[1],
+				Capacity:   util.StringToInt(match[2]),
+				Durability: util.StringToInt(match[3]),
+				Flavor:     util.StringToInt(match[4]),
+				Texture:    util.StringToInt(match[5]),
+				Calories:   util.StringToInt(match[6]),
+			}
+		})
+	}
+
+	util.TestRuns("15", reader, part1, part2)
+	util.SolutionRuns("15", reader, part1, part2)
+}

d15/test-runs/0.txt

@@ -0,0 +1,2 @@
+Butterscotch: capacity -1, durability -2, flavor 6, texture 3, calories 8
+Cinnamon: capacity 2, durability 3, flavor -2, texture -1, calories 3

util/combinatorics.go

@@ -45,3 +45,31 @@ func Permutations[T any](array []T) (permutations [][]T) {
 
 	return res
 }
+
+// Returns all combinations of N numbers that sums to M
+func CombinationsWithSum(length, targetSum int) [][]int {
+	var results [][]int
+	var current []int
+
+	var backtrack func(length, targetSum, start int, current []int)
+	backtrack = func(length, targetSum, start int, current []int) {
+		if len(current) == length {
+			if Sum(current) == targetSum {
+				cpy := make([]int, len(current))
+				copy(cpy, current)
+				results = append(results, cpy)
+			}
+			return
+		}
+
+		for i := 0; i <= targetSum; i++ {
+			current = append(current, i)
+			backtrack(length, targetSum, start+i, current)
+			current = current[:len(current)-1]
+		}
+	}
+
+	backtrack(length, targetSum, 0, current)
+
+	return results
+}