高精度加法器

Add.h

#include <string>
#include <iostream>
#pragma once
#ifndef ADD_H_
#define ADD_H_

// 高精度加法

class Add
{
private:
    int* data; // 数据, 从低位到高位排序
    int len;
public:
    Add() { data = nullptr; len = 0; }
    Add(const char* s);
    Add(const std::string& s);
    Add(const Add& a);
    Add& operator= (const Add& a);
    ~Add();
    friend Add operator+(const Add& A, const Add& B);
    friend Add& operator+=(Add& A, const Add& B);
    friend std::ostream& operator<<(std::ostream& os, const Add& B);
    friend std::istream& operator>>(std::istream& ins, Add& B);
    explicit operator std::string ();
};

#endif // !ADD_H_

Add.cpp

#include <iostream>
#include <cstring>
#include "Add.h"

using namespace std;

// 高精度加法

Add::Add(const char* s)
{
    len = strlen(s);
    data = new int[len];
    int i = 0;
    for (; i < len; i++)
    {
        data[i] = s[len - 1 - i] - '0';
    }
}

Add::Add(const std::string& s)
{
    len = s.length();
    data = new int[len];
    int i = 0;
    for (; i < len; i++)
    {
        data[i] = s[len - 1 - i] - '0';
    }
}

Add::Add(const Add& a)
{
    len = a.len;
    data = new int[len];
    int i = 0;
    for (; i < len; i++)
    {
        data[i] = a.data[i];
    }
}

Add& Add::operator= (const Add& a)
{
    len = a.len;
    data = new int[len];
    int i = 0;
    for (; i < len; i++)
    {
        data[i] = a.data[i];
    }
    return *this;
}

Add::~Add()
{
    delete[] data;
}

Add operator+(const Add& A, const Add& B)
{
    const Add* AB[2];
    if (A.len > B.len)
    {
        AB[0] = &A;
        AB[1] = &B;
    }
    else
    {
        AB[0] = &B;
        AB[1] = &A;
    }
    int* newnN = new int[AB[0]->len + 1];
    int i, tmp = 0;;
    for (i = 0; i < AB[1]->len; i++)
    {
        newnN[i] = tmp + AB[0]->data[i] + AB[1]->data[i];
        tmp = newnN[i] / 10;
        newnN[i] -= tmp * 10;
    }
    for (; i < AB[0]->len; i++)
    {
        newnN[i] = tmp + AB[0]->data[i];
        tmp = newnN[i] / 10;
        newnN[i] -= tmp * 10;
    }
    Add C;
    if (tmp == 1)
    {
        newnN[i] == tmp;
        C.data = newnN;
        C.len = AB[0]->len + 1;
    }
    else
    {
        C.data = newnN;
        C.len = AB[0]->len;
    }
    return C;
}

Add& operator+=(Add& A, const Add& B)
{
    A = A + B;
    return A;
}

std::ostream& operator<<(std::ostream& os, const Add& B)
{
    os << "\"";
    for (int i = 0; i < B.len; i++)
    {
        os << B.data[B.len - 1 - i] ;
    }
    os << "\"";
    return os;
}

std::istream& operator>>(std::istream& ins, Add& B)
{
    string s;
    ins >> s;
    B = s;
    return ins;
}

Add::operator std::string()
{
    string s;
    for (int i = 0; i < len; i++)
    {
        s += data[len - 1 - i] + '0';
    }
    return s;
}

Text.cpp

#include <iostream>
#include "Add.h"

using namespace std;

int main(void)
{
    Add a, b, c;
    cin >> a >> b;
    cout << a << endl
        << b << endl;
    c = a += b;
    cout << a << endl
        << b << endl
        << c << endl;
    string d = (string)c;
    cout << d << endl;
}

测试结果

123456789123456789123456789
12345678987654321
"123456789123456789123456789"
"12345678987654321"
"123456789135802468111111110"
"12345678987654321"
"123456789135802468111111110"
123456789135802468111111110