aoc2021/Sources/17/17.swift

//
//  File.swift
//
//
//  Created by Max Nuding on 17.12.21.
//

import Foundation
import Runner
import Collections

struct Point:Hashable {
    var x: Int
    var y: Int
}

struct Area {
    let topLeft: Point
    let botRight: Point
    
    init(x: String, y: String) {
        let xVals = x[x.index(x.startIndex, offsetBy: 2)...].components(separatedBy: "..").map { Int($0)! }
        let yVals = y[y.index(y.startIndex, offsetBy: 2)...].components(separatedBy: "..").map { Int($0)! }
        topLeft = Point(x: xVals.first!, y: yVals.last!)
        botRight = Point(x: xVals.last!, y: yVals.first!)
    }
    
    func contains(point: Point) -> Bool {
        point.x >= topLeft.x && point.x <= botRight.x && point.y <= topLeft.y && point.y >= botRight.y
    }
    
    func overshot(point: Point) -> Bool {
        point.y < botRight.y || point.x > botRight.x
    }
}

struct Probe {
    var position = Point(x: 0, y: 0)
    var velocity: Point
    
    mutating func move() {
        position.x += velocity.x
        position.y += velocity.y
        if velocity.x < 0 {
            velocity.x += 1
        } else if velocity.x > 0 {
            velocity.x -= 1
        }
        velocity.y -= 1
    }
}

class Day17: Runnable {
    let inputPath: String
    
    required init(inputPath: String) {
        self.inputPath = inputPath
    }
    
    public func run() {
        let input = try! String(contentsOfFile: inputPath)
        let parts = input
            .trimmingCharacters(in: .newlines)
            .components(separatedBy: ": ")
            .last!
            .components(separatedBy: ", ")
        let area = Area(x: parts.first!, y: parts.last!)
        
        var maxY = Int.min
        var found = [Point]()
        found.reserveCapacity(3000)
        for x in 0...500 {
            for y in -500...500 {
                let velocity = Point(x: x, y: y)
                var probe = Probe(velocity: velocity)
                var maxYCurrent = Int.min
                repeat {
                    probe.move()
                    if probe.position.y > maxYCurrent {
                        maxYCurrent = probe.position.y
                    }
                    if area.contains(point: probe.position) {
                        if maxYCurrent > maxY {
                            maxY = maxYCurrent
                        }
                        found.append(velocity)
                        break
                    }
                } while !area.overshot(point: probe.position)
            }
        }
        print(maxY)
        print(Set(found).count)
    }
}