project1.cpp

大数加减乘除的实现

        cout << endl;
        return ;
    }
    else                                               //用辗转相除求结果
    {
        for(iter = num1.begin(),i = 0; i < len2 ;++i,++iter)
            temp.push_back(*iter);
        list<char> digit,res;

        for(j = 0; j < 10; j++)
        {
                digit.clear();
                digit.push_back(j + '0');
                res = Mul(num2,digit);
                res = Sub(temp,res);
                if(*(res.begin()) == '-')
                    break;
        }
            //cout << endl;print(temp); cout << endl;
        j -= 1;

        if(j > 0)
        {
            digit.clear();
            digit.push_back(j + '0');
            temp = Sub(temp,num2);
            ans.push_back(j + '0');
        }
        
        for(;iter != num1.end();++iter)
        {
            temp.push_back(*iter);
            for(j = 0; j < 10; j++)
            {
                digit.clear();
                digit.push_back(j + '0');
                res = Mul(num2,digit);
                res = Sub(temp,res);
                if(*(res.begin()) == '-')
                    break;
            }
            //cout << endl;print(temp); cout << endl;
            j -= 1;
            digit.clear();
            digit.push_back(j + '0');
            res = Mul(num2,digit);
            temp = Sub(temp,res);
            ans.push_back(j + '0');
        }
        if(sign)
            ans.push_front('-');
    }
    cout << "商是";
    print(ans);
    cout << "；余数是" ;
    print(temp);
    cout << endl;
    return ;
}

void  Root(list<char> num1)                     //求大数的平方根，用枚举算法暴力搜索算法求
{
    list<char> ans;
    int len1;
    list<char> digit,temp;
    len1 = num1.size();
    int a = len1 / 2;                            //a是结果的最少位数
    int i;
    digit.push_back('1');
    ans.push_back('1');                        //从ans=10 ^ a 开始搜索
    for(i = 0; i < a - 1; i++)
        ans.push_back('0');
    while(true)                                  //搜到则结束
    {
        temp = Mul(ans,ans);
        temp = Sub(num1,temp);
        if(*(temp.begin()) == '-')                      //如果当前ans的平方大于num1，则得结果
            break;
        ans = Add(ans,digit);
    }
    ans = Sub(ans,digit);
    print(ans);
    cout << endl;

}
list<char> translate(string input)
{
    list<char> res;
    int len = input.length();
    for(int i = 0; i < len; i++)
        res.push_back(input[i]);
    return res;

}
void print(list<char> ans)
{
    list<char>::iterator iter;
    int flag = 1;
    iter = ans.begin();
    if(*iter == '-')
     {
        cout << *iter;
        iter++;
     }
    for(;iter != ans.end(); ++iter)
    {
        if(*iter == '0' && flag)
            continue;
            //cout << (*iter);
        else
        {
            flag = 0;
            cout << (*iter);
        }
    }
    if( flag == 1)
        cout << 0 ;;
    //cout << endl;
}
int main()
{
    char choice;         //选择要进行的运算
    list<char> num1;
    list<char> num2;
    list<char> res;
    string input;
    while(true)
    {
        cout << endl;
        printhelp();
        cin >> choice;
        switch(choice)
        {
            case '1':                      //如果选择加法运算
                cout << "请输入第一个数" << endl;
                cin >> input;
                num1 = translate(input);
                cout << "请输入第二个数" << endl;
                cin >> input;
                num2 = translate(input);
                res = Add(num1,num2);
                print(num1);
                cout << " + " ;
                print(num2);
                cout << " = ";
                print(res);
                cout << endl;
                break;
            case '2':                    //选择减法运算
                cout << "请输入第一个数" << endl;
                cin >> input;
                num1 = translate(input);
                cout << "请输入第二个数" << endl;
                cin >> input;
                num2 = translate(input);
                res = Sub(num1,num2);
                print(num1);
                cout <<" - " ;
                print(num2);
                cout << " = ";
                print(res);
                cout << endl;
                break;
            case '3':                  //选择乘法运算
                cout << "请输入第一个数" << endl;
                cin >> input;
                num1 = translate(input);
                cout << "请输入第二个数" << endl;
                cin >> input;
                num2 = translate(input);
                res = Mul(num1,num2);
                print(num1);
                cout <<" * " ;
                print(num2);
                cout << " = ";
                print(res);
                cout << endl;
                break;
            case '4':                      //选择除法运算
                cout << "请输入第一个数" << endl;
                cin >> input;
                num1 = translate(input);
                cout << "请输入第二个数" << endl;
                cin >> input;
                num2 = translate(input);
                print(num1);
                cout << " / " ;
                print(num2);
                cout << " = ";
                if(num2.size() == 1 && (*(num2.begin()) == '0'))
                {
                    cout << "divided zero error" << endl;
                    break;
                }
                Div(num1,num2);
                //print(res);
                cout << endl;
                break;
            case '5':                         //选择求根运算
                cout << "请输入第一个数" << endl;
                cin >> input;
                num1 = translate(input);
                if(*(num1.begin()) == '-')
                {
                    cout << "负数没有实数平方根" << endl;
                    break;
                }
                Root(num1);
                break;
            case '6':
                return 0;
            default:
                  break;
        }
    }
}