38. Count and Say

38. Count and Say.swift

class Solution {
    func countAndSay(_ n: Int) -> String {
        if n == 1 { return "1" }
        let val = countAndSay( n - 1 )
        let res = "\(count(String(val)))"
        return res
    }
    
    func count(_ str: String) -> String {
        guard str.count > 0 else {
            return "count is zero"
        }
        var cnt = 0
        var oldValue: Character = str.first!
        var resStr = ""
        
        for item in str {
            if item == oldValue {
                cnt += 1
            } else {
                resStr.append("\(cnt)\(oldValue)")
                cnt = 1
            }
            oldValue = item
        }
        resStr.append("\(cnt)\(oldValue)")

        return resStr
    }
}

let sol = Solution()
print(sol.countAndSay(5))