func subStrings(_ str: String) -> [String] {
  var subStrArray = [String]()
  for i in 0..<str.count {
    for j in stride(from: str.count-1, to: -1, by: -1){
      if (i > j){break}
      let startIdx = str.index(str.startIndex, offsetBy: i)
      let endIdx = str.index(str.startIndex, offsetBy: j)
      subStrArray.append(String(str[startIdx...endIdx]))
    }
  }
  return subStrArray
}
func findLongestSubStr(minLengthA minA: [String], maxLengthA maxA: [String]){
  var longestSubStr = ""
  var longestSubStrLength = 0
  for subStr in minA {
    if maxA.contains(subStr){
      if longestSubStrLength < subStr.count{
        longestSubStr = subStr
        longestSubStrLength = subStr.count
      }
    }
  }
  print("The longest common substring is \(longestSubStr) and is of length \(longestSubStrLength)")
}

let subStrArray1 = subStrings("GeeksforGeeks")
let subStrArray2 = subStrings("GeeksQuiz")


if subStrArray1.count < subStrArray2.count {
 findLongestSubStr(minLengthA: subStrArray1, maxLengthA: subStrArray2)
}
else {
  findLongestSubStr(minLengthA: subStrArray2, maxLengthA: subStrArray1)
}