109 lines
2.2 KiB
Go
109 lines
2.2 KiB
Go
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package solutions
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import (
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"strconv"
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"strings"
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)
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type Bag struct {
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color string
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contents []BagContent
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containsShinyGold bool
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}
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type BagContent struct {
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count int
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color string
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}
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// Given a bag statement string, returns its contents
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func parseBagStatement(bagStatement string) Bag {
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bagEndIndex := strings.Index(bagStatement, " bags contain ")
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bagColor := bagStatement[:bagEndIndex]
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bagContentsStr := bagStatement[bagEndIndex+14:]
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// if no aditional bags
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if bagContentsStr[:2] == "no" {
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return Bag{color: bagColor, contents: make([]BagContent, 0)}
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}
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// parse remainder bags
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bagsContained := strings.Split(bagContentsStr, ", ")
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bagContents := make([]BagContent, len(bagsContained))
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for idx, bag := range bagsContained {
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bagCount, err := strconv.Atoi(bag[:1])
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if err != nil {
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panic("expected a number, got `" + bag + "`")
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}
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bagStrIndex := strings.Index(bag, " bag")
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bagColor2 := bag[2:bagStrIndex]
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bagContents[idx] = BagContent{count: bagCount, color: bagColor2}
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}
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/*
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grammar for bag statements:
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statement = bag color, "bags contain", (bag list | empty bag), "."
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empty bag = "no other bags"
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bag list = bag declaration, bag declaration+
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bag declaration = number, bag color, "bag", "s"?
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bag color = word, word
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*/
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return Bag{color: bagColor, contents: bagContents}
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}
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func bagContainsShinyGold(bag *Bag, bagMap map[string]Bag) bool {
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if bag.containsShinyGold {
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return true
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}
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// recursively search
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for _, bagName := range bag.contents {
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if bagName.color == "shiny gold" {
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bag.containsShinyGold = true
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return true
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}
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nextBag := bagMap[bagName.color]
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if bagContainsShinyGold(&nextBag, bagMap) {
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bag.containsShinyGold = true
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return true
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}
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}
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return false
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}
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func Day07Part01(isTest bool) int {
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input := ReadInput("07", isTest)
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groups := strings.Split(input, "\n")
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bags := make(map[string]Bag)
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// parse and collect the bags
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for _, statement := range groups {
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parsedBag := parseBagStatement(statement)
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bags[parsedBag.color] = parsedBag
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}
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shinyGoldContainers := 0
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// process the bags
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for _, bag := range bags {
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if bagContainsShinyGold(&bag, bags) {
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shinyGoldContainers += 1
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}
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}
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return shinyGoldContainers
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}
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func Day07Part02(isTest bool) int {
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return -1
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}
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