面试题31：字符串正则表达式的递归匹配

mplement 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

class Solution {
public:
    bool isMatch(const char *s, const char *p) {

        if (*p == '') return *s == '';

        if (*(p + 1) == '*') {
            if (*s == *p || *p == '.') {
                if (*s == '') {
                    return isMatch(s, p + 2);
                } else {
                    return isMatch(s, p + 2) || isMatch(s + 1, p) || isMatch(s + 1, p + 2);
                }
            } else {
                return isMatch(s, p + 2);
            }
        }
        if (*s == *p || (*p == '.' && *s != '')) {
            return isMatch(s + 1, p + 1);
        }
        return false;
    }
};