프로그래머스 - 다트 게임 (카카오 블라인드 채용)

import Foundation

func solution(_ dartResult:String) -> Int {
    var dartResult = dartResult.map{ $0 }
    var pointStack: [Int] = []
    var tmpPoint = ""
    var optionCheck = false
    var savePoint = 0
    while !dartResult.isEmpty {
        let current = dartResult.first
        func saveAtStack() {
            pointStack.append(savePoint)
            savePoint = 0
            tmpPoint = ""
        }
                
        if current!.isNumber {
            while dartResult.first!.isNumber {
                tmpPoint += String(dartResult.removeFirst())
            }
        } else {
            if current == "S" {
                savePoint = Int(tmpPoint)!
                saveAtStack()
            } else if current == "D" {
                savePoint = Int(tmpPoint)! * Int(tmpPoint)!
                saveAtStack()
            } else if current == "T" {
                savePoint = Int(tmpPoint)! * Int(tmpPoint)! * Int(tmpPoint)!
                saveAtStack()
            } else if current == "*" {
                if !pointStack.isEmpty {
                    pointStack[pointStack.count - 1] *= 2
                }
                if pointStack.count > 1 {
                    pointStack[pointStack.count - 2] *= 2
                }
            } else if current == "#" {
                let lastPoint = pointStack.removeLast()
                pointStack.append(-lastPoint)
                savePoint = -savePoint
            }
            dartResult.removeFirst()
        }
    }
    
    return pointStack.reduce(0, +)
}