019-正则表达式匹配.cpp

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