day 21 backfill

This commit is contained in:
David 2020-12-22 19:52:52 -05:00
parent f744ac6745
commit 42c77627d1

138
21/main.go Normal file
View File

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