aoc2021/Sources/10/10.swift

//
//  File.swift
//
//
//  Created by Max Nuding on 05.12.21.
//

import Foundation
import Runner
import Collections


struct Day10: Runnable {
    let inputPath: String
    
    public func run() {
        let input = try! String(contentsOfFile: inputPath)
        let lines = input
            .trimmingCharacters(in: .newlines)
            .components(separatedBy: .newlines)
        var s = Deque<String.Element>()
        var illegalCharacters = [String.Element]()
        var autocompleteScores = [Int]()
        for line in lines {
            s = Deque<String.Element>()
            var isIllegalLine = false
            for char in line {
                if char.isClosing {
                    guard let popped = s.popFirst() else {
                        fatalError()
                    }
                    guard let shouldBeClosedBy = popped.closedBy else {
                        fatalError()
                    }
                    if shouldBeClosedBy == char {
                        continue // Valid chunk
                    }
                    //print("Line: \(lineNumber): Expected \(shouldBeClosedBy), but found \(char) instead")
                    illegalCharacters.append(char)
                    isIllegalLine = true
                    break
                }
                s.prepend(char)
            }
            if !isIllegalLine {
                var lineScore = 0
                while let last = s.popFirst() {
                    let charValue = last.closedBy!.autocompleteScore!
                    lineScore = lineScore * 5 + charValue
                }
                autocompleteScores.append(lineScore)
            }
        }
        print(illegalCharacters.map{$0.score!}.reduce(0,+))
        print(autocompleteScores.sorted()[autocompleteScores.count / 2])
    }
}

extension String.Element {
    var isClosing: Bool { self == "]" || self == ")" || self == ">" || self == "}" }
    var closedBy: String.Element? {
        switch self {
        case "[":
            return "]"
        case "(":
            return ")"
        case "{":
            return "}"
        case "<":
            return ">"
        default:
            return nil
        }
    }
        
    var score: Int? {
        switch self {
        case ")":
            return 3
        case "]":
            return 57
        case "}":
            return 1197
        case ">":
            return 25137
        default:
            return nil
        }
    }
    
    var autocompleteScore: Int? {
        switch self {
        case ")":
            return 1
        case "]":
            return 2
        case "}":
            return 3
        case ">":
            return 4
        default:
            return nil
        }
    }
}