647.Palindromic Substrings

1-Approach #1: Expand Around Center [Accepted]

O(n^2)

class Solution {
    public int countSubstrings(String s) {
        int n = s.length();
        int cnt = 0;
        for(int center = 0; center < 2 * n -1; center++){
            int left = center / 2;
            int right = left + center % 2;
            while(left >= 0 && right < n && s.charAt(left) == s.charAt(right)){
                cnt++;
                left--;
                right++;
            }
        }
        return cnt;
    }
}