Leetcode #13: Converts a number in roman numerals to an Integer. Assumes a valid roman numeral.

RomanToInt.swift

let romanMapping: [String: Int] = [
    "I" : 1,
    "V" : 5,
    "X" : 10,
    "L" : 50,
    "C" : 100,
    "D" : 500,
    "M" : 1000
]

func romanToInt(_ s: String) -> Int {
    var output = 0
    var lastCharStr = ""
    for character in s {
        let currenCharStr = String(character)
        guard let currentVal = romanMapping[currenCharStr] else {
            lastCharStr = ""
            continue
        }
        
        if let lastVal = romanMapping[lastCharStr] {
            if currentVal/10 == lastVal {
                let toAdd = currentVal - (lastVal * 2)
                output += toAdd
            }
            else if currentVal/5 == lastVal {
                let toAdd = currentVal - (lastVal * 2)
                output += toAdd
            }
            else {
                output += currentVal
            }
        }
        else {
            output += currentVal
        }
        
        lastCharStr = currenCharStr
    }
    
    return output
}