 /**
  * Question Link: https://leetcode.com/problems/longest-palindromic-substring/
- * Primary idea: 2D Dynamic Programming, update boolean array based on 
+ * Primary idea: 2D Dynamic Programming, update boolean array based on
  *               current two characters' equity and the previous boolean subarray
  * Time Complexity: O(n^2), Space Complexity: O(n^2)
  *
  */
 
 class LongestPalindromicSubstring {
-    func longestPalindrome(s: String) -> String {
+    func longestPalindrome(_ s: String) -> String {
         guard s.characters.count > 1 else {
             return s
         }

        
        return String(sChars[maxStart ... maxStart + maxLen - 1])
    }
}
        let len = sChars.count
        var maxLen = 1
        var maxStart = 0
        var isPalin = Array(repeating: Array(repeating: false, count : len), count : len)
        
        // set palindrome whose len is 1
        for i in 0 ... len - 1 {
