大整数类 模板

自己写的大整数模板，已经升级到V2.0

功能：

计算大整数加减乘数取模运算，支持无限位数，支持正负数输入输出及运算，支持判断两个大整数的大小

保障：

1.VC++2013，GCC4.7.3运行测试通过

2.学校OJ加减乘除取模均AC

//BigInt V2.0
//By KunSoft

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <cmath>
#include <deque>
#include <iterator>
#include <algorithm>
using namespace std;
typedef long long LLT;

class BigInt
{
public:
	BigInt() :negative(false) {}
	BigInt(const LLT);
	BigInt(const char*);
	BigInt(const string);
	BigInt(const BigInt & x);
	BigInt & operator = (const BigInt &);
	friend istream & operator >> (istream &, BigInt &);
	friend ostream & operator << (ostream &, BigInt);
	BigInt operator + (const BigInt &) const;
	BigInt operator - (const BigInt &) const;
	BigInt operator * (const BigInt &) const;
	BigInt operator / (const LLT &) const;
	LLT operator % (const LLT &) const;
	bool operator > (const BigInt &) const;
	bool operator == (const BigInt &) const;
	bool operator >= (const BigInt &) const;
	friend BigInt abs(const BigInt &);
	BigInt operator - () const;
private:
	deque<int> num;
	bool negative;
};

BigInt::BigInt(const LLT x){
	LLT t = abs(x);
	negative = x >= 0 ? true : false;
	while (t > 0){
		num.push_back(t % 10);
		t = t / 10;
	}
}
BigInt::BigInt(const char* str){
	unsigned i = str[0] == '-' ? 1 : 0;
	this->negative = str[0] == '-' ? true : false;
	for (; i < strlen(str); ++i) num.push_back(str[i] - '0');
}
BigInt::BigInt(const string str){
	unsigned i = str[0] == '-' ? 1 : 0;
	this->negative = str[0] == '-' ? true : false;
	for (; i < str.size(); ++i) num.push_back(str[i] - '0');
}
BigInt::BigInt(const BigInt &x){
	negative = x.negative;
	num = x.num;
}
BigInt & BigInt::operator = (const BigInt &x){
	negative = x.negative;
	num = x.num;
	return (*this);
}
istream & operator >> (istream &is, BigInt & x){
	string str; is >> str;
	x = str;
	return is;
}
ostream & operator << (ostream &os, BigInt x){
	if (x.negative) os << '-';
	for (unsigned i = 0; i != x.num.size(); ++i)
		os << x.num[i];
	return os;
}
bool BigInt::operator > (const BigInt & rhs) const {
	BigInt x = (*this), y = rhs;
	if (!x.negative && y.negative) return true;
	if (x.negative && !y.negative) return false;
	if (x.negative && y.negative) swap(x, y);
	if (x.num.size() > y.num.size()) return true;
	if (x.num.size() < y.num.size()) return false;
	for (unsigned i = 0; i != x.num.size(); ++i) {
		if (x.num[i] > y.num[i]) return true;
		if (x.num[i] < y.num[i]) return false;
	}
	return false;
}
bool BigInt::operator == (const BigInt & rhs) const {
	return negative == rhs.negative && num == rhs.num;
}
bool BigInt::operator >= (const BigInt & rhs) const {
	return *this > rhs || *this == rhs;
}
BigInt abs(const BigInt & rhs){
	BigInt res;
	res.negative = false;
	res.num = rhs.num;
	return res;
}
BigInt BigInt::operator - () const {
	BigInt ret = *this; ret.negative = !ret.negative;
	return ret;
}
BigInt BigInt::operator + (const BigInt & y) const {
	if (!this->negative && y.negative) return *this - abs(y);
	if (this->negative && !y.negative) return y - abs(*this);
	if (this->negative && y.negative) return -(abs(*this) + abs(y));
	BigInt x = *this, res;
	int temp = 0;
	for (int i = x.num.size() - 1, j = y.num.size() - 1; i >= 0 || j >= 0; --i, --j) {
		int a = i < 0 ? 0 : x.num[i];
		int b = j < 0 ? 0 : y.num[j];
		res.num.push_front((a + b + temp) % 10);
		temp = (a + b + temp) / 10;
	}
	if (temp != 0) res.num.push_front(temp);
	return res;
}
BigInt BigInt::operator * (const BigInt & y) const {
	deque<int> a, b, res;
	copy(this->num.begin(), this->num.end(), front_inserter(a));
	copy(y.num.begin(), y.num.end(), front_inserter(b));
	res.resize(a.size() + b.size() + 5);
	for (unsigned i = 0; i < a.size(); ++i) for (unsigned j = 0; j < b.size(); ++j)
		res[i + j] += a[i] * b[j];
	for (unsigned i = 0; i < res.size() - 1; ++i){
		res[i + 1] += res[i] / 10;
		res[i] %= 10;
	}
	while (res.size() >= 2 && res.back() == 0)
		res.pop_back();
	reverse(res.begin(), res.end());
	BigInt ret; ret.negative = this->negative ^ y.negative; ret.num = res;
	return ret;
}
BigInt BigInt::operator - (const BigInt & y) const {
	if (!this->negative && y.negative) return *this + abs(y);
	if (this->negative && !y.negative) return -(abs(*this) + y);
	if (this->negative && y.negative) return abs(y) - abs(*this);
	deque<int> a, b, res; BigInt ret;
	copy(this->num.begin(), this->num.end(), front_inserter(a));
	copy(y.num.begin(), y.num.end(), front_inserter(b));
	if (y > *this) swap(a, b), ret.negative = true;
	res.resize(max(a.size(), b.size()) + 5);
	for (unsigned i = 0, j = 0; i < a.size() || j < b.size(); ++i, ++j){
		int m = i < a.size() ? a[i] : 0;
		int n = j < b.size() ? b[j] : 0;
		res[i] = m - n;
	}
	for (unsigned i = 0; i < res.size() - 1; ++i) if (res[i] < 0) {
		res[i] += 10;
		--res[i + 1];
	}
	while (res.size() >= 2 && res.back() == 0)
		res.pop_back();
	reverse(res.begin(), res.end()); ret.num = res;
	return ret;
}
BigInt BigInt::operator / (const LLT & y) const {
	LLT temp = 0;
	BigInt x = (*this), res;
	for (unsigned i = 0; i < x.num.size(); ++i){
		temp = temp * 10 + x.num[i];
		res.num.push_back((int)(temp / y));
		temp %= y;
	}
	while (res.num.size() >= 2 && res.num.front() == 0)
		res.num.pop_front();
	return res;
}
LLT BigInt::operator % (const LLT & y) const {
	LLT res = 0;
	for (unsigned i = 0; i < this->num.size(); ++i)
		res = (res * 10 + this->num[i]) % y;
	return res;
}








int main()
{
	BigInt a, b;
	while (cin >> a >> b)
		cout << a + b << endl;
	return  0;
}

下面是老版的V1.0版本提供参考，使用数组实现，速度会快一些。

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <cmath>
#include <algorithm>
#define MAXN 1024
using namespace std;

class BigInt
{
private:
    int num[MAXN];
    int len;
    int flag;
public:
    BigInt()
    {
        memset(num, 0, sizeof(num));
        len = 0;
        flag = 1;
    };
    BigInt(const int);
    BigInt(const char*);
    BigInt(const string);
    BigInt(const BigInt &x);
    BigInt &operator = (const BigInt &);

    friend istream &operator >> (istream &, BigInt &);
    friend ostream &operator << (ostream &, BigInt &);

    BigInt operator + (const BigInt &);
    BigInt operator - (const BigInt &);
    BigInt operator * (const BigInt &);
    BigInt operator / (const long long int &);
    long long int operator % (const long long int &);
    bool operator > (const BigInt &);

    friend BigInt rev(const BigInt &x);
};

//将一个int类型的变量转化为BigInt类型
BigInt::BigInt(const int x)
{
    memset(num, 0, sizeof(num));
    len = 0;
    int t;
    if(x < 0)
    {
        t = -x;
        flag = -1;
    }
    else
        t = x;
    while (t > 0)
    {
        num[len++] = t % 10;
        t = t / 10;
    }
}

//将一个C风格字符串的变量转化为BigInt类型
BigInt::BigInt(const char* str)
{
    memset(num, 0, sizeof(num));
    len = strlen(str);
    for (int i = 0; i < len; i++)
    {
        num[i] = str[i] - '0';
    }
}

//将一个string字符串的变量转化为BigInt类型
BigInt::BigInt(const string str)
{
    string temp(str);
    memset(num, 0, sizeof(num));
    len = temp.size();
    int cnt = 0;
    for (string::iterator i = temp.begin(); i != temp.end(); i++)
        num[cnt++] = *i - '0';
}

//拷贝BigInt对象
BigInt::BigInt(const BigInt &x)
{
    len = x.len;
    flag = x.flag;
    memset(num, 0, sizeof(num));
    for (int i = 0; i < len; i++)
        num[i] = x.num[i];
}

//重载赋值运算符
BigInt & BigInt::operator = (const BigInt &x)
{
    len = x.len;
    flag = x.flag;
    memset(num, 0, sizeof(num));
    for (int i = 0; i < len; i++)
        num[i] = x.num[i];
    return (*this);
}

//重载输入运算符
istream &operator >> (istream &is, BigInt &x)
{
    string temp;
    is >> temp;
    memset(x.num, 0, sizeof(x.num));
    x.len = temp.size();
    int cnt = 0;
    for (string::iterator i = temp.begin(); i != temp.end(); i++)
        x.num[cnt++] = *i - '0';
    return is;
}

//重载输出运算符
ostream &operator << (ostream &os, BigInt &x)
{
    if(x.flag == -1)
        printf("-");
    for (int i = 0; i < x.len; i++)
        printf("%d", x.num[i]);
    return os;
}

//获取翻转BigInt后的BigInt
BigInt rev(const BigInt &x)
{
    BigInt res;
    res.len = x.len;
    res.flag = x.flag;
    memset(res.num, 0, sizeof(res.num));
    for(int i=0; i<res.len; i++)
        res.num[res.len-1-i] = x.num[i];
    return res;
}

//判断两个BigInt的大小
bool BigInt::operator > (const BigInt &y)
{
    BigInt x = (*this);
    if(x.len > y.len)
        return true;
    else if(x.len < y.len)
        return false;
    else if(x.len == y.len)
    {
        for(int i=0; i<x.len; i++)
        {
            if(x.num[i] > y.num[i])
                return true;
            else if(x.num[i] < y.num[i])
                return false;
        }
        return false;
    }
}

//两个BigInt之间的加法运算
BigInt BigInt::operator + (const BigInt &y)
{
    BigInt x(*this);
    BigInt res;
    int i, j;
    int cnt = 0, temp = 0;

    for (i = x.len - 1, j = y.len - 1; i >= 0 || j >= 0; i--, j--)
    {
        int a = i < 0 ? 0 : x.num[i];
        int b = j < 0 ? 0 : y.num[j];
        res.num[cnt++] = (a + b + temp) % 10;
        temp = (a + b + temp) / 10;
    }
    if (temp != 0)
        res.num[cnt++] = temp;
    res.len = cnt;

    for (int i = 0; i < (res.len / 2); i++)
    {
        int t = res.num[i];
        res.num[i] = res.num[res.len - 1 - i];
        res.num[res.len - 1 - i] = t;
    }
    return res;
}

//两个BigInt之间的乘法运算
BigInt BigInt::operator * (const BigInt &y)
{
    BigInt a, b, res;
    BigInt ret;
    a = rev(*this);
    b = rev(y);

    for(int i=0; i<a.len; i++)
        for(int j=0; j<b.len; j++)
            res.num[i+j] += a.num[i] * b.num[j];

    for(int i=0; i<MAXN-1; i++)
    {
        res.num[i+1] += res.num[i]/10;
        res.num[i] = res.num[i]%10;
    }

    for(int i = MAXN-1; i>=0; --i)
    {
        if(res.num[i]!=0)
        {
            res.len = i + 1;
            break;
        }
    }

    if(res.len==0)
    {
        res.len = 1;
        res.num[0] = 0;
    }

    ret = rev(res);
    return ret;
}

//两个BigInt之间的减法运算
BigInt BigInt::operator - (const BigInt &y)
{
    BigInt a = rev(*this), b = rev(y);
    BigInt res, ret;

    if(b > a)
    {
        swap(a, b);
        res.flag = -1;
    }

    for(int i=0, j=0; i<a.len || j<b.len; i++, j++)
    {
        int m = i<a.len ? a.num[i] : 0;
        int n = j<b.len ? b.num[j] : 0;
        res.num[i] = m - n;
    }

    for(int i=0; i<MAXN-1; i++)
    {
        if(res.num[i]<0)
        {
            res.num[i] += 10;
            res.num[i+1]--;
        }
    }

    for(int i = MAXN-1; i>=0; --i)
    {
        if(res.num[i]!=0)
        {
            res.len = i + 1;
            break;
        }
    }

    if(res.len==0)
    {
        res.len = 1;
        res.num[0] = 0;
    }

    ret = rev(res);
    return ret;
}

//BigInt除以一个长整形运算
BigInt BigInt::operator / (const long long int &y)
{
    long long int temp = 0;
    BigInt x = (*this);
    BigInt res;
    for(int i=0; i<len; i++)
    {
        temp = temp*10 + x.num[i];
        res.num[i] = temp / y;
        temp = temp % y;
    }

    //去前导0
    int cnt = 0;
    for(int i = 0; i<MAXN; ++i)
    {
        if(res.num[i]!=0)
        {
            cnt = i;
            break;
        }
    }
    for(int i = cnt; i<MAXN; ++i)
    {
        int t = res.num[i];
        res.num[i] = res.num[i-cnt];
        res.num[i-cnt] = t;
    }

    res.len = x.len - cnt;

    return res;
}

//BigInt对一个长整形做取余运算
long long int BigInt::operator % (const long long int &y)
{
    long long int temp = 0;
    BigInt x = (*this);
    BigInt res;
    for(int i=0; i<len; i++)
    {
        temp = temp*10 + x.num[i];
        res.num[i] = temp / y;
        temp = temp % y;
    }
    return temp;
}








int main()
{
    return  0;
}