Merge pull request #68 from tholok97/day7

Day 7 in Go

Author: Arxcis

days/day-07/solutions/tholok97.go

@@ -0,0 +1,99 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strconv"
+)
+
+type pair struct {
+	amount int
+	color  string
+}
+
+func main() {
+	scanner := bufio.NewScanner(os.Stdin)
+
+	rules := make(map[string][]pair)
+
+	for scanner.Scan() {
+		ruleString := scanner.Text()
+		color, contained := parseRule(ruleString)
+		rules[color] = contained
+	}
+
+	sum := 0
+
+	for key := range rules {
+		if contains(rules, key, "shiny gold") {
+			sum++
+		}
+	}
+
+	fmt.Println(sum)
+
+	// subtract one cost as we care about the cost of the bags **within** the
+	// initial bag
+	fmt.Println(colorCost(rules, "shiny gold") - 1)
+}
+
+func parseRule(s string) (color string, contained []pair) {
+	reBagColor := regexp.MustCompile(`^([\w ]*) bags contain`)
+	reBagColorMatches := reBagColor.FindStringSubmatch(s)
+	color = reBagColorMatches[1]
+	reNoOther := regexp.MustCompile(`no other bags`)
+
+	if reNoOther.MatchString(s) {
+		// No bags are contained, return early
+		return color, make([]pair, 0)
+	}
+
+	reBagContains := regexp.MustCompile(`(,? (\d+) ([\w ]*) bags?)`)
+	reBagContainsMatches := reBagContains.FindAllStringSubmatch(s, -1)
+	contained = make([]pair, len(reBagContainsMatches))
+
+	for i, matches := range reBagContainsMatches {
+		amount, err := strconv.Atoi(matches[2])
+
+		if err != nil {
+			panic("misbehaving number string >:(")
+		}
+
+		contained[i] = pair{
+			amount: amount, // don't care about this one
+			color:  matches[3],
+		}
+	}
+
+	return color, contained
+}
+
+// does 'color' contain 'target'?
+// assume X can't contain X
+func contains(rules map[string][]pair, color, target string) bool {
+	for _, contained := range rules[color] {
+		if contained.color == target {
+			return true
+		}
+
+		if contains(rules, contained.color, target) {
+			return true
+		}
+	}
+	return false
+}
+
+// what's the total cost of 'color'?
+func colorCost(rules map[string][]pair, color string) int {
+	// myself
+	cost := 1
+
+	for _, contained := range rules[color] {
+		// + the cost of each of my bags
+		cost += contained.amount * colorCost(rules, contained.color)
+	}
+
+	return cost
+}

days/day-07/test.sh

@@ -7,6 +7,7 @@ D=$(dirname $(realpath $0))
 echo ""
 echo "--- Day 7: Handy Haversacks ---"
 $D/../../languages/sml.sh    $D/input.txt $D/output.txt $D/solutions/day07.sml
+$D/../../languages/go.sh     $D/input.txt $D/output.txt $D/solutions/tholok97.go
 $D/../../languages/python.sh $D/input.txt $D/output.txt $D/solutions/day07.stektpotet.py
 $D/../../languages/node.sh   $D/input.txt $D/output.txt $D/solutions/day07.mjs
 echo ""