HDU-1018 Big Number

题目：

description：

In many applications very large integers numbers are required. Some  of these applications are using keys for secure transmission of data,  encryption, etc. In this problem you are given a number, you have to  determine the number of digits in the factorial of the number.

Input：

Input consists of several lines of integer numbers. The first line  contains an integer n, which is the number of cases to be tested,  followed by n lines, one integer 1 ≤ n ≤ 107 on each line.

Output：

The output contains the number of digits in the factorial of the integers appearing in the input.

Sample Input

2

10

20

Sample Output

7

19

解析：

1. 本题题意，求阶乘结果的位数

2. 本题其实就是一个数学公式解决。斯特林公式：lnN!=NlnN-N+0.5ln(2N*pi)

3. 百度百科链接

#include
#include
#define pi 3.1415926
int main()
{
    int ans,i,t,n;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        ans=(n*log(n)-n+0.5*log(2*n*pi))/log(10);
        ans+=1;
        printf("%d\n",ans);
    }
    return 0;
}