aoc2020/day21/day21.go

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strings"
)

type dish struct {
	ingredients []string
	allergens   []string
}

func readDish(line string) dish {
	var food dish
	parts := strings.Split(line, " (contains ")
	if len(parts) != 2 {
		log.Fatalf("Invalid line: %s", line)
	}

	for _, ing := range strings.Split(parts[0], " ") {
		food.ingredients = append(food.ingredients, ing)
	}

	cleanedPart2 := strings.TrimSuffix(parts[1], ")")
	for _, allergen := range strings.Split(cleanedPart2, ", ") {
		food.allergens = append(food.allergens, allergen)
	}

	return food
}

func readFile(file *os.File) []dish {
	var foods []dish
	scanner := bufio.NewScanner(file)

	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			break
		}

		foods = append(foods, readDish(line))
	}
	if err := scanner.Err(); err != nil {
		log.Fatalf("Scanner error: %s", err)
	}

	return foods
}

type ingredient struct {
	count             int
	possibleAllergens map[string]int
}

func processFoods(foods []dish) map[string]ingredient {
	processedIngredients := make(map[string]ingredient)

	for _, food := range foods {
		for _, item := range food.ingredients {
			var currentIngredient ingredient
			if _, ok := processedIngredients[item]; !ok {
				currentIngredient = ingredient{count: 0, possibleAllergens: make(map[string]int)}
			} else {
				currentIngredient = processedIngredients[item]
			}

			currentIngredient.count++
			for _, allergen := range food.allergens {
				currentIngredient.possibleAllergens[allergen]++
			}

			processedIngredients[item] = currentIngredient
		}
	}

	return processedIngredients
}

func part1(processedIngredients map[string]ingredient) int {
	sum := 0

	for _, item := range processedIngredients {
		countPossibleAllergens := 0

		for _, value := range item.possibleAllergens {
			countPossibleAllergens += value
		}

		if countPossibleAllergens <= item.count {
			sum += item.count
		}
	}

	return sum
}

func main() {
	if len(os.Args) < 2 {
		log.Fatal("You need to specify a file!")
	}

	filePath := os.Args[1]
	file, err := os.Open(filePath)
	if err != nil {
		log.Fatalf("Failed to open %s!\n", filePath)

	}

	foods := readFile(file)
	if err := file.Close(); err != nil {
		log.Fatalf("Failed to close file: %s", err)
	}

	processedIngredients := processFoods(foods)
	fmt.Println("Part1:", part1(processedIngredients))
}