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代码语言：javascript复制#include <cstring>
#include <string>
#include <iostream>
using namespace std;
constexpr auto MAXN = 9999;
constexpr auto MAXSIZE = 1000;
constexpr auto DLEN = 4;
class BigN
{
private:
int a[MAXSIZE / 20] = { 0 }; //可以控制大数的位数,越小性能越高，但支持的数字会变短
int len; //大数长度
public:
BigN() { len = 1; memset(a, 0, sizeof(a)); } //构造函数
BigN(const int&); //将一个int类型的变量转化为大数
BigN(const char*); //将一个字符串类型的变量转化为大数
BigN(const string&); //将一个字符串类型的变量转化为大数
BigN(const BigN&); //拷贝构造函数
//BigN(BigN&&) {}; //移动构造函数
BigN& operator()(const int&); //将一个int类型的变量转化为大数
BigN& operator()(const char*); //将一个字符串类型的变量转化为大数
BigN& operator()(const string&); //将一个字符串类型的变量转化为大数
BigN& operator()(const BigN&); //拷贝构造函数
//BigN& operator()(BigN&&) { return *this; }; //移动构造函数
//重载复制
BigN& operator=(const int&);
BigN& operator=(const char*);
BigN& operator=(const BigN&);
//BigN& operator=(BigN&&)noexcept { return *this; };//移动赋值
BigN& operator=(const string&);
//重载比较
bool operator>(const BigN&) const;
bool operator>(const int&)const;
bool operator>=(const BigN&) const;
bool operator<(const BigN&) const;
bool operator<(const int&)const;
bool operator<=(const BigN&) const;
bool operator==(const BigN&) const;
bool operator!=(const BigN&) const;
bool operator!() const;
//四则运算重载
BigN operator (const BigN&) const;
BigN operator ();
BigN operator (int);
BigN operator =(const BigN&);
BigN operator-(const BigN&) const;
BigN operator--();
BigN operator--(int);
BigN operator-=(const BigN&);
BigN operator*(const BigN&) const;
BigN operator*(const int&) const;
BigN operator*=(const BigN&);
BigN operator/(const BigN&) const;
BigN operator/(const int&) const;
BigN operator/=(const BigN&);
BigN operator^(const int&) const; //大数的n次方运算
int operator%(const int&) const; //大数对一个int类型的变量进行取模运算
void display(); //输出大数
friend istream& operator>>(istream&, BigN&); //重载输入运算符
friend ostream& operator<<(ostream&, const BigN&); //重载输出运算符
};
BigN::BigN(const int &b) //将一个int类型的变量转化为大数
{
int c, d = b;
len = 0;
while (d > MAXN)
{
c = d - (d / (MAXN 1)) * (MAXN 1);
d = d / (MAXN 1);
a[ len] = c;
}
a[ len] = d;
}
BigN::BigN(const char* s) //将一个字符串类型的变量转化为大数
{
int t, k, index, l, i;
l = strlen(s);
len = l / DLEN;
if (l % DLEN)
len;
index = 0;
for (i = l - 1; i >= 0; i -= DLEN)
{
t = 0;
k = i - DLEN 1;
if (k < 0)
k = 0;
for (int j = k; j <= i; j)
t = t * 10 s[j] - '0';
a[ index] = t;
}
}
BigN::BigN(const string& s)
{
int t, k, index, l, i;
l = s.size();
len = l / DLEN;
if (l % DLEN)
len;
index = 0;
for (i = l - 1; i >= 0; i -= DLEN)
{
t = 0;
k = i - DLEN 1;
if (k < 0)
k = 0;
for (int j = k; j <= i; j)
t = t * 10 s[j] - '0';
a[ index] = t;
}
}
BigN::BigN(const BigN& T) : len(T.len) //拷贝构造函数
{
int i;
for (i = 0; i < len; i)
a[i] = T.a[i];
}
BigN& BigN::operator=(const BigN& n) //重载赋值运算符，大数之间进行赋值运算
{
int i;
len = n.len;
memset(a, 0, sizeof(a));
for (i = 0; i < len; i)
a[i] = n.a[i];
return *this;
}
istream& operator>>(istream& in, BigN& b) //重载输入运算符
{
char ch[MAXSIZE * 4];
int i = -1;
in >> ch;
int l = strlen(ch);
int count = 0, sum = 0;
for (i = l - 1; i >= 0;)
{
sum = 0;
int t = 1;
for (int j = 0; j < 4 && i >= 0; j, --i, t *= 10)
{
sum = (ch[i] - '0') * t;
}
b.a[count] = sum;
count;
}
b.len = count;
return in;
}
ostream& operator<<(ostream& out, const BigN& b) //重载输出运算符
{
int i;
out << b.a[b.len - 1];
for (i = b.len - 2; i >= 0; i--)
{
out.width(DLEN);
out.fill('0');
out << b.a[i];
}
return out;
}
BigN& BigN::operator()(const int& b)
{
int c, d = b;
len = 0;
while (d > MAXN)
{
c = d - (d / (MAXN 1)) * (MAXN 1);
d = d / (MAXN 1);
a[len ] = c;
}
a[ len] = d;
return *this;
}
BigN& BigN::operator()(const char* s)
{
int t, k, index, l, i;
l = strlen(s);
len = l / DLEN;
if (l % DLEN)
len;
index = 0;
for (i = l - 1; i >= 0; i -= DLEN)
{
t = 0;
k = i - DLEN 1;
if (k < 0)
k = 0;
for (int j = k; j <= i; j)
t = t * 10 s[j] - '0';
a[ index] = t;
}
return *this;
}
BigN& BigN::operator()(const string& s)
{
int t, k, index, l, i;
l = s.size();
len = l / DLEN;
if (l % DLEN)
len ;
index = 0;
for (i = l - 1; i >= 0; i -= DLEN)
{
t = 0;
k = i - DLEN 1;
if (k < 0)
k = 0;
for (int j = k; j <= i; j )
t = t * 10 s[j] - '0';
a[index ] = t;
}
return *this;
}
BigN& BigN::operator()(const BigN& T)
{
int i;
for (i = 0; i < len; i )
a[i] = T.a[i];
return *this;
}
BigN BigN::operator (const BigN& T) const //两个大数之间的相加运算
{
BigN t(*this);
int i, big; //位数
big = T.len > len ? T.len : len;
for (i = 0; i < big; i)
{
t.a[i] = T.a[i];
if (t.a[i] > MAXN)
{
t.a[i 1];
t.a[i] -= MAXN 1;
}
}
if (t.a[big] != 0)
t.len = big 1;
else
t.len = big;
return t;
}
BigN BigN::operator-(const BigN& T) const //两个大数之间的相减运算
{
int i, j, big;
bool flag;
BigN t1, t2;
if (*this > T)
{
t1 = *this;
t2 = T;
flag = 0;
}
else
{
t1 = T;
t2 = *this;
flag = 1;
}
big = t1.len;
for (i = 0; i < big; i)
{
if (t1.a[i] < t2.a[i])
{
j = i 1;
while (t1.a[j] == 0)
j;
--t1.a[--j];
while (j > i)
t1.a[--j] = MAXN;
t1.a[i] = MAXN 1 - t2.a[i];
}
else
t1.a[i] -= t2.a[i];
}
t1.len = big;
while (t1.a[t1.len - 1] == 0 && t1.len > 1)
{
--t1.len;
--big;
}
if (flag)
t1.a[big - 1] = 0 - t1.a[big - 1];
return t1;
}
BigN BigN::operator*(const BigN& T) const //两个大数之间的相乘运算
{
BigN ret;
int i, j, up;
int temp, temp1;
for (i = 0; i < len; i)
{
up = 0;
for (j = 0; j < T.len; j)
{
temp = a[i] * T.a[j] ret.a[i j] up;
if (temp > MAXN)
{
temp1 = temp - temp / (MAXN 1) * (MAXN 1);
up = temp / (MAXN 1);
ret.a[i j] = temp1;
}
else
{
up = 0;
ret.a[i j] = temp;
}
}
if (up != 0)
ret.a[i j] = up;
}
ret.len = i j;
while (ret.a[ret.len - 1] == 0 && ret.len > 1)
--ret.len;
return ret;
}
BigN BigN::operator/(const int& b) const //大数对一个整数进行相除运算
{
BigN ret;
int i, down = 0;
for (i = len - 1; i >= 0; --i)
{
ret.a[i] = (a[i] down * (MAXN 1)) / b;
down = a[i] down * (MAXN 1) - ret.a[i] * b;
}
ret.len = len;
while (ret.a[ret.len - 1] == 0 && ret.len > 1)
--ret.len;
return ret;
}
int BigN::operator %(const int& b) const //大数对一个int类型的变量进行取模运算
{
int i, d = 0;
for (i = len - 1; i >= 0; --i)
{
d = ((d * (MAXN 1)) % b a[i]) % b;
}
return d;
}
BigN BigN::operator^(const int& n) const //大数的n次方运算
{
BigN t, ret(1);
int i;
if (n < 0)
exit(-1);
if (n == 0)
return 1;
if (n == 1)
return *this;
int m = n;
while (m > 1)
{
t = *this;
for (i = 1; i << 1 <= m; i <<= 1)
{
t = t * t;
}
m -= i;
ret = ret * t;
if (m == 1)
ret = ret * (*this);
}
return ret;
}
bool BigN::operator>(const BigN& T) const //大数和另一个大数的大小比较
{
int ln;
if (len > T.len)
return true;
else if (len == T.len)
{
ln = len - 1;
while (a[ln] == T.a[ln] && ln >= 0)
--ln;
if (ln >= 0 && a[ln] > T.a[ln])
return true;
else
return false;
}
else
return false;
}
bool BigN::operator >(const int& t) const //大数和一个int类型的变量的大小比较
{
BigN b(t);
return *this > b;
}
void BigN::display() //输出大数
{
int i;
cout << a[len - 1];
for (i = len - 2; i >= 0; --i)
{
cout.width(DLEN);
cout.fill('0');
cout << a[i];
}
cout << endl;
}
#include <time.h>
int main()
{
int i = 2000000;
BigN a, b, c;
cin >> a >> b;
time_t t1 = clock();
while (--i) {
c = a * b;
}
time_t t2 = clock();
cout << t2 - t1 << endl;
cout << c << endl;
return 0;
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