[Swift] 프로그래머스_시저 암호

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<문제>

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<풀이>

func solution(_ s:String, _ n:Int) -> String {
    let upperStr = Array("abcdefghijklmnopqrstuvwxyz".uppercased())
    let lowerStr = Array("abcdefghijklmnopqrstuvwxyz")
    var result = ""
    
    for i in s {
        // 대문자에 포함된 경우
        if upperStr.contains(i) {
            var indexNum = (upperStr.firstIndex(of: i) ?? 0) + n
            
            if indexNum > 25 {
                indexNum = indexNum - 26
            }
            
            result.append(upperStr[indexNum])
        // 소문자에 포함된 경우
        } else if lowerStr.contains(i) {
            var indexNum = (lowerStr.firstIndex(of: i) ?? 0) + n
            
            if indexNum > 25 {
                indexNum = indexNum - 26
            }
            
            result.append(lowerStr[indexNum])
        } else {
            result.append(i)
        }
    }
    return result
}

print(solution("AB", 1)) // BC
print(solution("z", 1)) // a
print(solution("a B z", 4)) // e F d