HDU 3123 GCC

Problem Description

The GNU Compiler Collection (usually shortened to GCC) is a compiler system produced by the GNU Project supporting various programming languages. But it doesn’t contains the math operator “!”.
In mathematics the symbol represents the factorial operation. The expression n! means "the product of the integers from 1 to n". For example, 4! (read four factorial) is 4 × 3 × 2 × 1 = 24. (0! is defined as 1, which is a neutral element in multiplication, not multiplied by anything.)
We want you to help us with this formation: (0! + 1! + 2! + 3! + 4! + ... + n!)%m

Input

The first line consists of an integer T, indicating the number of test cases.
Each test on a single consists of two integer n and m.

Output

Sample Input

110 861017

Sample Output

593846

思路：当n!大于等于m的时候，肯定可以整除m，所以我们只需要计算n！<m

#include <iostream>#include<cstdio>#include<cstring>using namespace std;int main(){   int icase;   int m;   char n[105];   scanf("%d",&icase);   while(icase--)   {       scanf("%s %d",n,&m);       int num,t;       if(strlen(n)>=7)  //m的最大数值对应的长度          t=m;       else          sscanf(n,"%d",&t);        long long mid=1,sum=1;        for(int i=1;i<=t;i++)        {            mid=((mid%m)*(i%m))%m;    //计算阶乘            sum=(sum%m+mid%m)%m;       //阶乘的相加        }        printf("%lld\n",sum%m);   }    return 0;}