65 lines
1.2 KiB
Swift
65 lines
1.2 KiB
Swift
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import Foundation
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let input = loadData(day: 10)
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let scanner = Scanner(string: input)
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var adapters = scanner.integers()!.sorted { $0 > $1 }
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adapters.append(0)
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let device = adapters[0] + 3
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var current = device
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var ones = 0
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var threes = 0
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for adapter in adapters {
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let step = current - adapter
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if step == 3 {
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threes += 1
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} else if step == 1 {
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ones += 1
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} else if step != 2 {
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print("fail")
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}
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current = adapter
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}
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print("part 1", ones * threes)
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struct Key: Hashable {
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var start: Int
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var max: Int
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}
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var memo: [Key: Int] = [:]
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func findPaths(start: Int, max: Int) -> Int {
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if let value = memo[Key(start: start, max: max)] {
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return value
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}
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let diff = max - adapters[start]
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if diff > 3 || diff < 1 {
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return 0
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}
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if start == adapters.count - 1 {
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return 1
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}
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var result = 0
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for n in (start + 1)..<(adapters.count) {
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let next = findPaths(start: n, max: adapters[start])
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if next == 0 {
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break
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}
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result += next
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}
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memo[Key(start: start, max: max)] = result
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return result
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}
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print(findPaths(start: 0, max: device))
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