PalindromicSubstrings.java

//Given a string, your task is to count how many palindromic substrings in this string.
//The substrings with different start indexes or end indexes are counted as different substrings 
//even they consist of same characters.

//Example 1:
//Input: "abc"
//Output: 3
//Explanation: Three palindromic strings: "a", "b", "c".
//Example 2:
//Input: "aaa"
//Output: 6
//Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".
//Note:
//The input string length won't exceed 1000.

class PalindromicSubstrings {
    int result = 0;
    public int countSubstrings(String s) {
        if(s == null || s.length() == 0) {
            return 0;
        }
        
        for(int i = 0; i < s.length(); i++) {
            extendPalindrome(s, i, i);
            extendPalindrome(s, i, i + 1);
        }
        
        return result;
    }
    
    public void extendPalindrome(String s, int left, int right) {
        while(left >= 0 && right < s.length() && s.charAt(left) == s.charAt(right)) {
            result++;
            left--;
            right++;
        }
    }
}