c++大数模板
2017-07-24 13:48:25         来源：为AI而奋斗

```//支持正数的运算。两数相减也要为正数
#include
#include
using namespace std;
const int MAXN=10000;
struct bign
{
int len, s[MAXN];
bign ()
{
memset(s, 0, sizeof(s));
len = 1;
}
bign (int num) { *this = num; }
bign (const char *num) { *this = num; }
bign operator = (const int num)
{
char s[MAXN];
sprintf(s, "%d", num);
*this = s;
return *this;
}
bign operator = (const char *num)
{
for(int i = 0; num[i] == '0'; num++) ;  //去前导0
len = strlen(num);
for(int i = 0; i < len; i++) s[i] = num[len-i-1] - '0';
return *this;
}
bign operator + (const bign &b) const //+
{
bign c;
c.len = 0;
for(int i = 0, g = 0; g || i < max(len, b.len); i++)
{
int x = g;
if(i < len) x += s[i];
if(i < b.len) x += b.s[i];
c.s[c.len++] = x % 10;
g = x / 10;
}
return c;
}
bign operator += (const bign &b)
{
*this = *this + b;
return *this;
}
void clean()
{
while(len > 1 && !s[len-1]) len--;
}
bign operator * (const bign &b) //*
{
bign c;
c.len = len + b.len;
for(int i = 0; i < len; i++)
{
for(int j = 0; j < b.len; j++)
{
c.s[i+j] += s[i] * b.s[j];
}
}
for(int i = 0; i < c.len; i++)
{
c.s[i+1] += c.s[i]/10;
c.s[i] %= 10;
}
c.clean();
return c;
}
bign operator *= (const bign &b)
{
*this = *this * b;
return *this;
}
bign operator - (const bign &b)
{
bign c;
c.len = 0;
for(int i = 0, g = 0; i < len; i++)
{
int x = s[i] - g;
if(i < b.len) x -= b.s[i];
if(x >= 0) g = 0;
else
{
g = 1;
x += 10;
}
c.s[c.len++] = x;
}
c.clean();
return c;
}
bign operator -= (const bign &b)
{
*this = *this - b;
return *this;
}
bign operator / (const bign &b)
{
bign c, f = 0;
for(int i = len-1; i >= 0; i--)
{
f = f*10;
f.s[0] = s[i];
while(f >= b)
{
f -= b;
c.s[i]++;
}
}
c.len = len;
c.clean();
return c;
}
bign operator /= (const bign &b)
{
*this  = *this / b;
return *this;
}
bign operator % (const bign &b)
{
bign r = *this / b;
r = *this - r*b;
return r;
}
bign operator %= (const bign &b)
{
*this = *this % b;
return *this;
}
bool operator < (const bign &b)
{
if(len != b.len) return len < b.len;
for(int i = len-1; i >= 0; i--)
{
if(s[i] != b.s[i]) return s[i] < b.s[i];
}
return false;
}
bool operator > (const bign &b)
{
if(len != b.len) return len > b.len;
for(int i = len-1; i >= 0; i--)
{
if(s[i] != b.s[i]) return s[i] > b.s[i];
}
return false;
}
bool operator == (const bign &b)
{
return !(*this > b) && !(*this < b);
}
bool operator != (const bign &b)
{
return !(*this == b);
}
bool operator <= (const bign &b)
{
return *this < b || *this == b;
}
bool operator >= (const bign &b)
{
return *this > b || *this == b;
}
string str() const
{
string res = "";
for(int i = 0; i < len; i++) res = char(s[i]+'0') + res;
return res;
}
};

istream& operator >> (istream &in, bign &x)
{
string s;
in >> s;
x = s.c_str();
return in;
}

ostream& operator << (ostream &out, const bign &x)
{
out << x.str();
return out;
}
int main(){
bign a,b;
cin>>a;
cout<
```