gistfile1.txt

class Solution {
    func longestSubstring(_ s: String, _ k: Int) -> Int {
        let s = s.lowercased()

        var info = [Int](repeating: 0, count: 26)
        let chars = Array(s.utf8CString).map { Int($0 - "a".utf8CString.first!) }.filter{ $0 >= 0 }

        for c in chars {
            info[c] += 1
        }

        var valid = Set<Int>()
        for i in 0 ..< 26 {
            if info[i] >= k {
                valid.insert(i)
            }
        }

        var maxLen = 0

        let validNums = Array(valid).sorted()
        print(validNums)
        if validNums.count == 0 {
            return 0
        }
        var len = 0
        var temp = [Int](repeating: 0, count: validNums.count)
        for i in 0 ..< chars.count {
            if valid.contains(chars[i]) {
                temp[validNums.firstIndex(of: chars[i])!] += 1
                len += 1
                if isValid(temp, k) {
                    maxLen = max(maxLen, len)
                }
            } else {
                if isValid(temp, k) {
                    len = 0
                    temp = [Int](repeating: 0, count: validNums.count)
                    continue
                } else {
                    temp = [Int](repeating: 0, count: validNums.count)
                    maxLen = max(maxLen, longestSubstring(String((s as NSString).substring(with: NSMakeRange(i - len, len)).reversed()), k))
                    len = 0
                }
            }
        }

        return maxLen
    }

    func isValid(_ info: [Int], _ k: Int) -> Bool {
        for i in info {
            if i < k && i != 0 {
                return false
            }
        }

        return true
    }
}