需要重载输入，输出，构造函数，以及比较操作符

用两个双端队列分别存储整数与小数部分数据，输入输出过程均转成字符串。

Bignumber实现代码

using size_t =unsigned long;private:    const int POWER = 4;//压四位存储    std::string str_num,str_float_num;    std::deque
    
     num;    std::deque
     
      float_num;    bool mark = 0;public:    Bignumber()=default;    Bignumber(std::string& item){        this->to_Bignumber(item);    }    Bignumber(double item){        char *ch;        std::string buf;        //std::cout<
      
       <
       
        <
        
         to_Bignumber(buf);    }    ~Bignumber() = default;    std::string to_string(){        std::string ret;        if(mark)ret.push_back('-');        char ch[5];        sprintf(ch,"%d",num.front());        ret += ch;        for(int i = num.size();i > 1;--i){            sprintf(ch,"%04d",num[i-1]);            ret += ch;        }        ret.push_back('.');        sprintf(ch,"%d",float_num.front());        ret+=ch;        for(int i = 2;i <= float_num.size();++i){            sprintf(ch,"%04d",float_num[i-1]);            ret += ch;        }        return ret;    }    void to_Bignumber (std::string &st) {       if(st[0] == '-') {           mark = 1;           st.erase(0,1);//处理负数       }       int dot_pos = st.find_first_of('.');//处理小数点              str_num = st.substr(0,dot_pos);        str_float_num = st.substr(dot_pos+1,st.length() - 1 - dot_pos);               int len = (str_num.length() - 1) / POWER + 1;              for(int i = 0;i < len; ++i) {            int x = 0;            int end = str_num.length() - i * POWER;            int start = 0 > (end - POWER)?0:(end - POWER);            sscanf(str_num.substr(start,            end-start).c_str(),"%d", &x);            num.push_front(x);       }       len = (str_float_num.length() - 1) /POWER + 1;       for(int i = 0;i < len; ++i){            int x = 0;            int end = str_float_num.length() - i * POWER;            int start = 0 > (end - POWER)?0:(end - POWER);            sscanf(str_float_num.substr(start,end-start).c_str(), "%d", &x);            float_num.push_front(x);       }    }        bool operator <(const Bignumber &other) {//重载小于号        if(this == &other) return false;//如果地址相同直接返回假        if(num.size()
         
          other.num.size())return false; auto i = num.end(); auto j = other.num.end(); --i;--j; for(;i>=num.begin();i--,j--){ if(*i > *j)return false; } i = float_num.end(); j = other.float_num.end(); --i;--j; for(;i>=float_num.begin() && j>=other.float_num.begin();i--,j--){ if(*i > *j)return false; } return true; } bool operator ==(const Bignumber &other){//重载等于号 if(this == &other) return true; if(mark != other.mark)return false; if(!(num.size() == other.num.size())) return false; if(!(float_num.size() == other.float_num.size()))return false; for(int i = num.size() -1;i >= 0;++i){ if(!(num[i] == other.num[i])) return false; } for(int i = float_num.size()-1;i>=0;++i){ if(!(float_num[i] == other.float_num[i]))return false; } return true; } bool operator <=(const Bignumber &other){ if(this == &other) return true; return (*this < other || *this == other); } bool operator >(const Bignumber &other){ if(this == &other) return false; return !(*this <= other); } bool operator >=(const Bignumber &other){ if(this == &other) return true; return *this > other || *this==other; } bool operator !=(const Bignumber &other){ if(this == &other) return false; return !(*this == other); } Bignumber &operator =(const Bignumber &other){ if(this == &other) return *this; this->mark = other.mark; this->float_num = other.float_num; this->num = other.num; this->str_num = other.str_num; return *this; } Bignumber &operator =(const double &item){ char *ch; std::string buf; std::sprintf(ch, "%.10lf",item); buf = ch; to_Bignumber(buf); return *this; }std::ostream& operator <<(std::ostream &fout, Bignumber &item){ fout<
          
           >(std::istream &fin, Bignumber &item){ std::string temp; fin>>temp;//输入 item.to_Bignumber(temp); return fin; } 复制代码