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

If the next character of p is not *: check current *s and *p, and recursive search.
If the next character of p is *: search all possibilities.

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