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

需要注意*的意义，需要与前一个字符组合,如a*,表示0个a或者多个a

代码（递归）

class Solution {
public:
	static bool isMatch(string s, string p) {
		if (p.empty())
			return s.empty();
		if (p.size() > 1 && p[1] == '*'){
			return isMatch(s, p.substr(2)) || (!s.empty() && (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p));
		}
		else{
			return !s.empty() && (s[0] == p[0] || p[0] == '.') && isMatch(s.substr(1), p.substr(1));
		}
		return true;
	}
};