如何计算n！ 有几位数字

一个公式

#include<cstdio>#include<cstring>#include<algorithm>#include<map>#include<stack>#include<queue>#include<set>#include<vector>#include<cmath>#include<math.h>using namespace std;int main(){    int X;    scanf("%d",&X);    while(X--){        double n;        scanf("%lf",&n);        if(n == 1) printf("1\n");        else{        double ans = ((n * log(n)) - n + 0.5 * log(2 * n * 3.14159265))/log(1.0 * 10);        int t = (int)(ans + 1);        printf("%d\n",t);        }    }    return 0;}