FB面经 Prepare: All Palindromic Substrings

Given a string, calculate how many substring is palindrome. Ignore non-char characters. Ignore case;

Ex: "A@,b123a", equals "Aba", should output 4: "A", "b", "a", "Aba"

Spread from center: Like LC 5: longest palindromic substring

 package fb;

 public class Palindrome {
     public int countSubStr(String input) {
         if (input==null || input.length()==0) return 0;
         int res = 0;
         for (int i=0; i<input.length(); i++) {
             if (!isAlpha(input, i)) continue;
             res += helper(input, i, i);
             if (i < input.length()-1) res += helper(input, i, i+1);
         }
         return res;
     }

     public int helper(String s, int l, int r) {
         int res = 0;
         while (l>=0 && r<s.length()) {
             while (l>=0 && !isAlpha(s, l)) l--;
             while (r<s.length() && !isAlpha(s, r)) r++;
             if (l<0 || r>=s.length() || !isSame(s, l, r)) break;
             else {
                 res++;
                 l--;
                 r++;
             }
         }
         return res;
     }

     public boolean isAlpha(String s, int i) {
         char c = s.charAt(i);
         if (c>='a' && c<='z' || c>='A' && c<='Z') return true;
         return false;
     }

     public boolean isSame(String s, int l, int r) {
         char ll = s.charAt(l);
         char rr = s.charAt(r);
         ll = Character.isUpperCase(ll)? (char)(ll-'A'+'a') : ll;
         rr = Character.isUpperCase(rr)? (char)(rr-'A'+'a') : rr;
         return ll==rr;
     }

     /**
      * @param args
      */
     public static void main(String[] args) {
         // TODO Auto-generated method stub
         Palindrome sol = new Palindrome();
         String input = "A@,b123a";
         //String input = "Aba";
         int res = sol.countSubStr(input);
         System.out.println(res);

     }

 }