hdu 1018 (Big Number)

Problem 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

题意:给你n组数据,每组数据一个数,求这个数的阶乘问你这个数的阶乘是几位数

#include<math.h>
#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>

using namespace std;
const int maxn=1001;
typedef long long ll;
const int inf=0x3f3f3f3f;

double reback(int n)
{
    double cnt=0;
    for(int i=2; i<=n; i++)
    {
        cnt+=log10(i);
    }
    return cnt;
}

int main()
{
    int cas,n;
    scanf("%d",&cas);
    while(cas--)
    {
        scanf("%d",&n);
        printf("%d
",(int)reback(n)+1);
    }
    return 0;
}