75 lines
2 KiB
Swift
75 lines
2 KiB
Swift
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import Foundation
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let input = loadData(day: 7)
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let scanner = Scanner(string: input)
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struct Rule {
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var count: Int
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var color: String
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}
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extension Scanner {
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func scanRule() -> Rule? {
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guard let count = scanInt(),
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let color = scanUpToString(count == 1 ? " bag" : " bags"),
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scanString(count == 1 ? "bag" : "bags") != nil
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else { return nil }
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return Rule(count: count, color: color)
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}
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func scanRuleSet() -> (String, [Rule])? {
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guard
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let color = scanUpToString(" bags contain"),
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scanString("bags contain") != nil else { return nil }
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if scanString("no other bags.") != nil {
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return (color, [])
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}
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var rules: [Rule] = []
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repeat {
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guard let rule = scanRule() else { return nil }
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rules.append(rule)
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} while scanString(",") != nil
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guard scanString(".") != nil else { return nil }
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return (color, rules)
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}
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func scanAllRules() -> [String: [Rule]]? {
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var result: [String: [Rule]] = [:]
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while !isAtEnd {
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guard let (color, rules) = scanRuleSet() else { return nil }
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result[color] = rules
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}
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return result
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}
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}
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guard let rules = scanner.scanAllRules() else { fatalError() }
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//print(rules)
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func findPath(rules: [String: [Rule]], from: String, to: String) -> Bool {
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guard let from = rules[from] else { return false }
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if from.contains(where: { $0.color == to }) {
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return true
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}
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return from.contains(where: { findPath(rules: rules, from: $0.color, to: to) })
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}
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let count = rules.lazy.filter { findPath(rules: rules, from: $0.key, to: "shiny gold") }.count
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print("count", count)
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func bagsInside(rules: [String: [Rule]], color: String) -> Int {
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guard let from = rules[color] else { return 0 }
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return from.reduce(0) { accum, bag in
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accum + bag.count + bag.count * bagsInside(rules: rules, color: bag.color)
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}
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}
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print("total bags", bagsInside(rules: rules, color: "shiny gold"))
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