19：正则表达式匹配

pattern:a*abcd
str:abcd

class Solution {
public:
    bool match(char* str, char* pattern)
    {
        if(!str||!pattern)return false;
        return matchCore(str,pattern);
    }
    bool matchCore(char* str,char* pattern)
    {
        if(*str=='\0'&&*pattern=='\0')return true;
        if(*str!='\0'&&*pattern=='\0')return false;
        if(*(pattern+1)=='*')
        {
            if(*str==*pattern||(*pattern=='.'&&*str!='\0'))
                return matchCore(str,pattern+2)||matchCore(str+1,pattern);//见上方例子
            else return matchCore(str,pattern+2);
        }
        else{
            if(*str==*pattern||(*pattern=='.'&&*str!='\0'))
                return matchCore(str+1,pattern+1);
            else return false;
        }
    }
};