Regular Expression Matching

Implement regular expression matching with support for '.' and '*'.

'.' Matches any single character.
'*' Matches zero or more of the preceding element.

The matching should cover the entire input string (not partial).

The function prototype should be:
bool isMatch(const char *s, const char *p)

Some examples:
isMatch("aa","a") → false
isMatch("aa","aa") → true
isMatch("aaa","aa") → false
isMatch("aa", "a*") → true
isMatch("aa", ".*") → true
isMatch("ab", ".*") → true
isMatch("aab", "c*a*b") → true

public class Solution {
    public boolean isMatch(String s, String p) {
        if (p.length() == 0) {
        	return s.length() == 0;
        }
        if (p.length()==1 || p.charAt(1)!='*') {
        	if (s.length()< 1 || (p.charAt(0)!=s.charAt(0)&&p.charAt(0)!='.')) {
        		return false;
        	} else {
        		return isMatch(s.substring(1), p.substring(1));
        	}
        } else {
        	if (isMatch(s, p.substring(2))) {
        		return true;
        	}
        	int i = 0;
        	while (i<s.length() && (s.charAt(i)==p.charAt(0)||p.charAt(0)=='.')) {
        		if (isMatch(s.substring(i+1), p.substring(2))) {
        			return true;
        		}
        		i++;
        	}
        	return false;
        }
    }
}