hdu1042

#include<iostream>
#include<stdio.h>
#include<string>
#include<iomanip>
#include<algorithm>
using namespace std;
#include "time.h"

const int MAX_GROUPS = 20000;//最多2万组，每组最多4位整数，即最多可容纳8万位整数
const int MAXN = 9999;//每组的上限值
const int GROUP_LEN = 4;//每组的最大长度

class BigInteger
{
private:
int data[MAX_GROUPS];
int len;
void init()
{
memset(data,0,sizeof(data));
}
public:
BigInteger()
{
init();
len = 0;
}
BigInteger(const int b);
BigInteger(const BigInteger &);

bool operator > (const BigInteger&)const;
BigInteger & operator=(const BigInteger &);
BigInteger & add(const BigInteger &);
BigInteger & sub(const BigInteger &);
BigInteger operator+(const BigInteger &) const;
BigInteger operator-(const BigInteger &) const;
BigInteger operator*(const BigInteger &) const;
BigInteger operator/(const int &) const;
void print();
};
BigInteger::BigInteger(const int num)
{
int res,tmp = num;
len = 0;
init();
while(tmp > MAXN)
{
res = tmp - tmp / (MAXN + 1) * (MAXN + 1);
tmp = tmp / (MAXN + 1);
data[len++] = res;
}
data[len++] = tmp;
}
BigInteger::BigInteger(const BigInteger & rhs) : len(rhs.len)
{
int i;
init();
for(i = 0 ; i < len ; i++)
{
data[i] = rhs.data[i];
}
}
bool BigInteger::operator > (const BigInteger &rhs)const
{
int ln;
if(len > rhs.len)
{
return true;
}
else if(len < rhs.len)
{
return false;
}
else if(len == rhs.len)
{
ln = len - 1;
while(data[ln] == rhs.data[ln] && ln >= 0)
{
ln--;
}
if(ln >= 0 && data[ln] > rhs.data[ln])
{
return true;
}
else
{
return false;
}
}

}

BigInteger & BigInteger::operator = (const BigInteger &rhs)
{
init();
len = rhs.len;
for(int i = 0 ; i < len ; i++)
{
data[i] = rhs.data[i];
}
return *this;
}
BigInteger& BigInteger::add(const BigInteger &rhs)
{
int i,nLen;

nLen = rhs.len > len ? rhs.len : len;
for(i = 0 ; i < nLen ; i++)
{
data[i] = data[i] + rhs.data[i];
if(data[i] > MAXN)
{
data[i + 1]++;
data[i] = data[i] - MAXN - 1;
}
}
if(data[nLen] != 0)
{
len = nLen + 1;
}
else
{
len = nLen;
}

return *this;
}
BigInteger & BigInteger::sub(const BigInteger &rhs)
{
int i,j,nLen;
if (len > rhs.len)
{
for(i = 0 ; i < nLen ; i++)
{
if(data[i] < rhs.data[i])
{
j = i + 1;
while(data[j] == 0) j++;
data[j]--;
--j;
while(j > i)
{
data[j] += MAXN;
--j;
}
data[i] = data[i] + MAXN + 1 - rhs.data[i];
}
else
{
data[i] -= rhs.data[i];
}
}
len = nLen;
while(data[len - 1] == 0 && len > 1)
{
--len;
}
}
else if (len == rhs.len)
{
for(i = 0 ; i < len ; i++)
{
data[i] -= rhs.data[i];
}
while(data[len - 1] == 0 && len > 1)
{
--len;
}
}
return *this;
}
BigInteger BigInteger::operator+(const BigInteger & n) const
{
BigInteger a = *this;
a.add(n);
return a;
}
BigInteger BigInteger::operator-(const BigInteger & T) const
{
BigInteger b = *this;
b.sub(T);
return b;
}
BigInteger BigInteger::operator * (const BigInteger &rhs) const
{
BigInteger result;
int i,j,up;
int temp,temp1;

for(i = 0; i < len; i++)
{
up = 0;
for(j = 0; j < rhs.len; j++)
{
temp = data[i] * rhs.data[j] + result.data[i + j] + up;
if(temp > MAXN)
{
temp1 = temp - temp / (MAXN + 1) * (MAXN + 1);
up = temp / (MAXN + 1);
result.data[i + j] = temp1;
}
else
{
up = 0;
result.data[i + j] = temp;
}
}
if(up != 0)
{
result.data[i + j] = up;
}
}
result.len = i + j;
while(result.data[result.len - 1] == 0 && result.len > 1) result.len--;
return result;
}
BigInteger BigInteger::operator/(const int & b) const
{
BigInteger ret;
int i,down = 0;

for(i = len - 1 ; i >= 0 ; i--)
{
ret.data[i] = (data[i] + down * (MAXN + 1)) / b;
down = data[i] + down * (MAXN + 1) - ret.data[i] * b;
}
ret.len = len;
while(ret.data[ret.len - 1] == 0) ret.len--;
return ret;
}
void BigInteger::print()
{
int i;

cout << data[len - 1];
for(i = len - 2 ; i >= 0 ; i--)
{
cout.width(GROUP_LEN);
cout.fill('0');
cout << data[i];
}
cout << endl;
}
int main()
{
clock_t   start,   finish;
double     duration;
int i,n;
BigInteger result,num;
scanf("%d",&n);
start   =   clock();
result = BigInteger(1);
for(i = 2;i <= n; ++i)
{
num = BigInteger(i);
result = result * num;
}
result.print();
finish   =   clock();
duration   =   (double)(finish   -   start)   /   CLOCKS_PER_SEC;
printf(   "%f   seconds\n",   duration   );
return 0;
}