[LeetCode] #10 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

本题采用迭代求解。时间：29ms。代码如下：

class Solution {
public:
    bool isMatch(const char *s, const char *p){
        if (s == NULL || p == NULL) return false;
        if (*p == '') return *s == '';

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