3.6RegularExpressionMatching

Notes:
	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
	Solution: Both of the two solutions are from http://leetcode.com/2011/09/regular-expression-matching.html .
	Solution 3: DP.
	Solution 4: DP. O(n^2) Time, O(n) Space.
	*/

bool machcore(char *str, char *pattern)
{
	if (str == NULL || pattern == NULL)
	 	return false;
	if (*str == '\0'&&*pattern == '\0')
		return true;
	if ((*str != '\0'&&*pattern == '\0'))
		return false;
	if (*(pattern + 1) == '*')
	{
		if (*str == *pattern || *pattern == '.'&&*str != '\0')
			return machcore(str + 1, pattern + 2) || machcore(str + 1, pattern
			) || machcore(str, pattern + 2);
		else
			return machcore(str, pattern + 2);

	}
	if (*str == *pattern || *pattern == '.'&&*str != '\0')
		return machcore(str + 1, pattern + 1);
	return false;

}