LeetCode 010 Regular Expression Matching

题目描述：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

代码如下：

class Solution {
public:
    bool isMatch(const char *s, const char *p) {

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

        //如果下一个字符不是*，那么就需要匹配当前的字符！
        if(*(p + 1) != '*'){

            //下一个字符相等，或者有一个是'.'，则匹配成功
            if(*p == *s || (*p == '.' && *s != '\0'))
                return isMatch(s + 1, p + 1);
            else
                return false;
        }

        //下一个字符是*，则当前字符可以为0个或多个！
        else{
            while(*p == *s || (*p == '.' && *s != '\0')){
                if(isMatch(s, p + 2))
                    return true;
                s++;
            }
            return isMatch(s, p + 2);
        }

    }
};