Legionaries: In the range 1-13 (1,2,3,4,5,6,7,8,9,10,11,12,13) the digit 1 occurs 6 times. In the range, 1 - 2,660 (half the number of Romans in a legion), expressed in Roman numerals, how many times does the numeral “X” occur?

RomanNumbers.playground

import Foundation

func toRoman(number: Int) -> String {
    let romanValues = ["M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"]
    let arabicValues = [1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1]

    var romanValue = ""
    var startingValue = number

    for (index, romanChar) in romanValues.enumerated() {
        let arabicValue = arabicValues[index]
        let div = startingValue / arabicValue

        if (div > 0) {
            for _ in 0..<div {
                romanValue += romanChar
            }
            startingValue -= arabicValue * div
        }
    }
    return romanValue
}

func getCountOfCharacter(c: Character, stringArray: [String]) -> Int {
    let joined = stringArray.joined()
    return joined.filter { $0 == c }.count
}

/*
 
 Legionaries:
 
 In the range 1-13 (1,2,3,4,5,6,7,8,9,10,11,12,13) the digit 1 occurs 6 times.
 In the range, 1 - 2,660 (half the number of Romans in a legion), expressed in Roman numerals, how many times does the numeral “X” occur?
 
 */

var romanArray = [String]()
for i in 1...2660 {
    romanArray.append(toRoman(number: i))
}

let result = getCountOfCharacter(c: "X", stringArray: romanArray)
print(result)

// answer: 3977