Prob 1423 求大整数阶乘的位数

由斯特林[striling]公式可得：
lnN!=NlnN－N+0.5ln(2N*pi)
而N!的位数m = ceil(log10(N!))+1
ceil函数取上界，即不小于某数的最小整数
log10(N!) = lnN!/ln10

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define PI 3.14159265
static int striling(int m);
int main(int argc, char **argv)
{
        int m, n, i;
        int res[10];

        scanf("%d", &n);
        getchar();
        for(i = 0; i < n; i++){
                scanf("%d", &m);
                getchar();
                res[i] = striling(m);
        }

        for(i = 0; i < n; i++){
                printf("%d\n", res[i]);
        }

        exit(0);
}

static int striling(int m)
{
        int len;

        if((m == 1) || (m == 0)){
                return 1;
        }
        len = ceil((m*log(m)-m+(log(2*m*PI))/2)/log(10));

        return len;
}