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

方法：递归

递归逐个字符比较：每次要比较的时候先判断比较的字符后面的一个字符是不是‘*‘, 例如A=aa和B=a**b是否匹配的时候，在判断第一个字符是否匹配之前先判断B中第二字符是否为‘*‘。

class Solution {
public:
	bool isMatch(const char *s, const char *p)
	{
		if (*p == '\0') return *s == '\0';
		//next char is not '*':must match current character
		if (*(p + 1) != '*')
		{
			if (*p == *s || (*p == '.'&&*s != '\0'))
				return isMatch(s + 1, p + 1);
			else
				return false;
		}

		//next char is '*'
		if (*(p + 1) == '*')
		{
			while (*p == *s || (*p == '.') && *s != '\0')
			{
				if (isMatch(s, p + 2))
					return true;
				s++;
			}
			return isMatch(s, p + 2);
		}
	}
};

leetcode.10------------Regular Expression Matching