Regular Expression Matching 正则匹配问题

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

class Solution {
public:
    bool isMatch(const char *s,const char *p) {
        // Note: The Solution object is instantiated only once and is reused by each test case.    
        if(p == NULL)
            return s!=NULL?false:true;
        if(*p == '')
            return *s == '';
        if(*(p+1) == '*')
        {
            while(*s==*p || (*p=='.' && (*s)!='') )
            {
                if(isMatch(s,p+2) )
                    return true;
                ++s;
            }
            return isMatch(s,p+2);
        }
        else
        {
            if(*s==*p || (*p=='.'&&(*s)!='') )
                return isMatch(s+1,p+1);
            else
                return false;
        }
    }
};

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