[LeetCode] Regular Expression Matching(递归)

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) {

        if (*p == '\0') return *s == '\0';  //empty

        if (*(p + ) != '*') {//without *

            if(!matchFirst(s,p))

                return false;

            return isMatch(s + , p + );

        } else { //next: with a *

            if(isMatch(s, p + ))

                return true;    //try the length of 0

            while ( matchFirst(s,p) )       //try all possible lengths

                if (isMatch(++s, p + ))

                    return true;

        }

    }

private:

    bool matchFirst(const char *s, const char *p){

        return (*p == *s || (*p == '.' && *s != '\0'));

    }

};