day 21 backfill
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f744ac6745
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42c77627d1
138
21/main.go
Normal file
138
21/main.go
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@ -0,0 +1,138 @@
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package main
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import (
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"bufio"
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"fmt"
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"os"
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"strings"
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"time"
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)
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func main() {
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start := time.Now()
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partOne()
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duration := time.Since(start)
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partTwo()
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duration2 := time.Since(start)
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fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
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}
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type food struct {
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allergens []string
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ingredients []string
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}
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func intersection(a, b []string) []string {
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// special-case starting out
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if len(a) == 0 {
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return b
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} else if len(b) == 0 {
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return a
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}
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result := []string{}
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for _, s := range b {
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for _, t := range a {
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if s == t {
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result = append(result, s)
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}
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}
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}
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return result
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}
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func countSafeIngredients(f food, allergens map[string][]string) int {
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for c, i := range f.ingredients {
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for _, l := range allergens {
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for _, a := range l {
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if i == a {
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f.ingredients[c] = ""
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}
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}
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}
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}
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result := 0
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for _, i := range f.ingredients {
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if i != "" {
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result = result + 1
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}
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}
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return result
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}
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func remove(ingredients []string, ingredient string) []string {
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for i, j := range ingredients {
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if j == ingredient {
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ingredients[i] = ingredients[len(ingredients)-1]
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ingredients[len(ingredients)-1] = ""
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return ingredients[:len(ingredients)-1]
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}
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}
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return ingredients
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}
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func partOne() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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foods := []food{}
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allergens := map[string][]string{}
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for scanner.Scan() {
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line := strings.Split(scanner.Text(), " (contains ")
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f := food{
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ingredients: strings.Split(line[0], " "),
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allergens: strings.Split(strings.TrimSuffix(line[1], ")"), ", "),
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}
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foods = append(foods, f)
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for _, a := range f.allergens {
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allergens[a] = intersection(f.ingredients, allergens[a])
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}
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}
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sum := 0
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for _, f := range foods {
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sum = sum + countSafeIngredients(f, allergens)
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}
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fmt.Println(sum)
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}
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func partTwo() {
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f, _ := os.Open("input")
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reader := bufio.NewReader(f)
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scanner := bufio.NewScanner(reader)
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foods := []food{}
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allergens := map[string][]string{}
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for scanner.Scan() {
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line := strings.Split(scanner.Text(), " (contains ")
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f := food{
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ingredients: strings.Split(line[0], " "),
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allergens: strings.Split(strings.TrimSuffix(line[1], ")"), ", "),
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}
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foods = append(foods, f)
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for _, a := range f.allergens {
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allergens[a] = intersection(f.ingredients, allergens[a])
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}
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}
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// hey, this is the same reduction logic as day 16!
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trueAllergens := map[string]string{}
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var lastAllergenSolved string
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for i := 0; i < len(allergens); i = i + 1 {
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for i, a := range allergens {
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if len(a) == 1 {
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trueAllergens[i] = a[0]
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lastAllergenSolved = a[0]
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}
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}
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for i := range allergens {
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allergens[i] = remove(allergens[i], lastAllergenSolved)
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}
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}
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// formatting the result correctly is left as an exercise for the reader
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// because I don't want to deal with go's map order randomization
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fmt.Println(trueAllergens)
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}
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