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HDU 1018（数学题）
题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1018
Big Number
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others) Total Submission(s): 27548 Accepted Submission(s): 12526
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
题目大意：求一个数阶乘的位数。
分析：原本以为是一道大数题，其实是一道简单的数学题，需要用到“斯特灵”公式，log(n!)=log1 + log2 + ... + logn。
斯特灵公式链接：http://zh.wikipedia.org/wiki/%E6%96%AF%E7%89%B9%E9%9D%88%E5%85%AC%E5%BC%8F
1 #include <cstdio> 2 #include <cmath> 3 using namespace std; 4 5 int main () 6 { 7 int n,m,i; 8 double sum; 9 scanf ("%d",&n);10 while (n--)11 {12 scanf ("%d",&m);13 sum = 0;14 for (i=1; i<=m; i++)15 {16 sum += log10((double)i);17 }18 printf ("%d\n",(int)sum+1);19 }20 return 0;21 }
HDU 1018（数学题）
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