2020 Day 21 Complete

2020/day21/main.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+func main() {
+	fmt.Println("# Day 21")
+	inp := h.StdinToStringSlice()
+	solve(inp)
+}
+
+func solve(inp []string) {
+	var allergens []string
+	var ings []string
+	allergenToIng := make(map[string][]string)
+	for k := range inp {
+		pts := strings.Split(inp[k], " (contains ")
+		if len(pts) > 1 {
+			pts[1] = strings.TrimSuffix(pts[1], ")")
+		}
+		dishIngs := strings.Split(pts[0], " ")
+		ings = h.UnionStringSlice(dishIngs, ings)
+		algns := strings.Split(pts[1], ", ")
+		allergens = h.UnionStringSlice(algns, allergens)
+		for ak := range algns {
+			prev := allergenToIng[algns[ak]]
+			if len(prev) == 0 {
+				allergenToIng[algns[ak]] = dishIngs
+			} else {
+				allergenToIng[algns[ak]] = h.IntersectStringSlice(prev, dishIngs)
+			}
+		}
+	}
+	sort.Strings(allergens)
+	found := make(map[string]string)
+	for len(allergenToIng) > 0 {
+		for a, i := range allergenToIng {
+			if len(i) == 1 {
+				found[a] = i[0]
+				delete(allergenToIng, a)
+			}
+		}
+		for a, i := range allergenToIng {
+			// Remove all found allergens
+			for f := range found {
+				if k := h.StringSliceIndex(i, found[f]); k > -1 {
+					allergenToIng[a] = append(i[:k], i[k+1:]...)
+				}
+			}
+		}
+	}
+	var badIngs []string
+	for f := range found {
+		badIngs = append(badIngs, found[f])
+		if k := h.StringSliceIndex(ings, found[f]); k > -1 {
+			ings = append(ings[:k], ings[k+1:]...)
+		}
+	}
+	var total int
+	for k := range inp {
+		food := strings.Fields(strings.Split(inp[k], " (contains")[0])
+		for fk := range food {
+			for j := range ings {
+				if food[fk] == ings[j] {
+					total++
+				}
+			}
+		}
+	}
+	fmt.Printf("## Part 1:\nAnswer: %d\n", total)
+	badIngs = []string{}
+	for k := range allergens {
+		badIngs = append(badIngs, found[allergens[k]])
+	}
+	fmt.Printf("## Part 2:\nAnswer:\n%s\n", strings.Join(badIngs, ","))
+}