题解 | #将字符串转化为整数#

public:
    int atoi(const char *str) {
        int n = 0,result = 0;
        bool positive= true;
        if(str==NULL)
            return -1;
        while(*(str+n)!=NULL)
        {
            if(*(str+n)>='0'&&*(str+n) <='9')
            {
                result = result*10 + *(str+n) - '0';
            }
            else if(result!=0)
            {  
               return result*(positive) -result*(!positive); 
            }
            else if(*(str+n) =='-')
            {
               positive=!positive; 
            }
            n++;
        }
        return result*(positive) -result*(!positive);  
    }
};