p5

 
public class  {
    public int max = 1;
	public int l = 0;
	public int r = 0;

	public String longestPalindrome(String s) {

		if (s.length() < 1)
			return null;
		char[] c = s.toCharArray();
		for (int i = 0; i < c.length; i++) {
			dp(i, i + 1, c, 0);
			dp(i - 1, i + 1, c, 1);
		}
		return s.substring(l, r + 1);
	}

	public void dp(int left, int right, char[] c, int count) {

		if (left < 0 || right >= c.length || c[left] != c[right]) {
			if (count > max) {
				l = left + 1;
				r = right - 1;
				max = count;
			}
			return;
		}
		dp(left - 1, right + 1, c, count + 2);
	}
}