[LeetCode]wildcard matching通配符实现之递归

leetcode这道题还挺有意思的，实现通配符，'?'匹配任意字符，'*'匹配任意长度字符串，晚上尝试了一下，题目如下：

---

Implement wildcard pattern matching with support for '?' and '*'.

'?' Matches any single character.
'*' Matches any sequence of characters (including the empty sequence).

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", "*") → true
isMatch("aa", "a*") → true
isMatch("ab", "?*") → true
isMatch("aab", "c*a*b") → false

---

直接的思路很简单，两个字符串从头开始匹配，不匹配直接返回false，匹配，则两个指针都加1，匹配子字符串，所以自然而然就想用递归来实现。
复杂一点的是*号，匹配任意长度的字符串，所以*的判断也可以循环的递归isMatch判断*后的子字符串。实现如下：

class Solution {
public:
    bool isMatch(const char *s, const char *p) {
        if ('' == *s && '' == *p)
        {
            return true;
        }
        if ('*' == *s)
        {
            return asteriskMatch(s, p);
        }
        if ('*' == *p)
        {
            return asteriskMatch(p, s);
        }
        if (*s == *p || '?' == *s || '?' == *p)
        {
            s++;
            p++;
            return isMatch(s, p);
        }
        else
        {
            return false;
        }
    }
private:
    bool asteriskMatch(const char *asterisk, const char *p)
    {
        asterisk++;
        if ('*' == *asterisk)
        {
            return asteriskMatch(asterisk, p);
        }
        while (*p != '')
        {
            if (isMatch(asterisk, p))
            {
                return true;
            }
            p++;
        }
        if ('' == *asterisk && '' == *p)
        {
            return true;
        }
        return false;
    }
};

这样实现代码比较清爽，但是*的判断效率明显不高，提交，果然Time Limit Exceeded.没通过的用例是：

Last executed input:

"abbabaaabbabbaababbabbbbbabbbabbbabaaaaababababbbabababaabbababaabbbbbbaaaabababbbaabbbbaabbbbababababbaabbaababaabbbababababbbbaaabbbbbabaaaabbababbbbaababaabbababbbbbababbbabaaaaaaaabbbbbaabaaababaaaabb", "**aa*****ba*a*bb**aa*ab****a*aaaaaa***a*aaaa**bbabb*b*b**aaaaaaaaa*a********ba*bbb***a*ba*bb*bb**a*b*bb"

应该改用动态规划或者贪心法试试，不过总是觉得用递归实现比较优雅，而且看Discuss里很多人用DP也还是TLE，不行了，太困了，明天再改吧