Big Number(hdu1018,求n!的位數)
連結: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): 21347 Accepted Submission(s): 9607
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
Source
Asia 2002, Dhaka (Bengal)
Recommend
JGShining
解析:
求n階層的數位
n的位數=log10(n)+1;
n!的位數:
log10(sqrt(2*pi*n))+n*log10(n/e)+1;
0MS 256K 367 B C++
*/
#include<stdio.h> #include<string.h> #include<math.h> #include <iostream> using namespace std; const double pi=acos(-1.0); double e=exp(1.0);//注意e的取值 int main() { int T; double n; scanf("%d",&T); while(T--) { scanf("%lf",&n); int ans; ans=(int)(0.5*log10(2.0*pi*n)+n*log10(n/e))+1; printf("%d\n",ans); } return 0; }