HOJ 1296 Big Number

http://acm.hit.edu.cn/hoj/problem/view?id=1296

计算n!的位数

斯特灵公式:

n!≈sqrt(2*pi*n)*(n/e)^n

#include <stdio.h>#include <math.h>const double e = 2.7182818284590452354, pi = acos(-1);int main(){    int n;    int cases, dig;    double fac;    scanf("%d", &cases);    while (cases--)    {        scanf("%d", &n);        fac = log10( sqrt(2*pi*n)) + n*log10(n/e);        dig = ceil(fac);        printf("%d\n", dig);    }    return 0;}