// MARK: - 340. Longest Substring with At Most K Distinct Characters
// s = "eceba", k = 2
// 3 --> "ece" which its length is 3

// Словарь и скользящее окно. Словарь надо уменьшать и удалять ключ когда count == 0

func lengthOflongestSubStringK(_ s: String, k: Int) -> Int {
    var s = Array(s)
    var lettersDict = [Character:Int]()
    var l = 0
    var longest = 0

    for r in 0..<s.count {

        lettersDict[s[r], default: 0] += 1

        while lettersDict.count > k {
            lettersDict[s[l]]! -= 1
            if lettersDict[s[l]] == 0 {
                lettersDict[s[l]] = nil
            }
            l += 1
        }

        longest = max(longest, r - l + 1)
    }
    return longest
}

lengthOflongestSubStringK("eceba", k: 2)
lengthOflongestSubStringK("aabacccac", k: 2)