func stringToInt(_ string: String) -> Int {
    let digitVal: [Character : Int] = ["0": 0, "1": 1, "2": 2, "3": 3, "4": 4, "5": 5, "6": 6, "7": 7, "8": 8, "9": 9]

    var negative = false
    var result = 0

    for char in string {
        if let digit = digitVal[char] {
            result = result * 10 + digit
        }
        else if char == "-" {
            negative = true
        }
    }

    return negative ? -result : result
}