10000以内的阶乘

#include <iostream>#include <cmath>#include <stdio.h>using namespace std;/* 算法很水的，不过改良方向大概就是每四位算一个之类的东西了。。参考麦森数 */int getWeishu(int n){    double weishu = 0;    for(int i = 2; i <= n; i++)    {        weishu += log10(i);    }    return (int)weishu + 1;}int main(){    int digit[40000] = {0};    digit[0] = 1;    int n;    cin >> n;    int weishu = getWeishu(n);    for(int i = 2; i <= n; i++)    {        for(int j = 0; j < weishu + 1; j++)        {            digit[j] *= i;        }        if(i % 2 == 0)        {            for(int j = 0; j < weishu + 1; j++)            {                if(digit[j] >= 10)                {                    int ten = digit[j] / 10;                    digit[j + 1] += ten;                    digit[j] %= 10;                }            }        }    }    for(int j = 0; j < weishu + 1; j++)    {        if(digit[j] >= 10)        {            int ten = digit[j] / 10;            digit[j + 1] += ten;            digit[j] %= 10;        }    }    int outline = weishu;    if(weishu % 50 != 0)        outline = (weishu / 50 + 1) * 50;    outline -= 1;    for(int i = outline; i >= 0; i--)    {        printf("%d", digit[i]);        if(i % 50 == 0)            printf("\n");    }    return 0;}