杭电acm 3132GCC(简单数论)

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GCC

Time Limit: 1000/1000 MS (Java/Others)    Memory Limit: 131072/131072 K (Java/Others)
Total Submission(s): 5140    Accepted Submission(s): 1716


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
Output the answer of (0! + 1! + 2! + 3! + 4! + ... + n!)%m.

Constrains
0 < T <= 20
0 <= n < 10^100 (without leading zero)
0 < m < 1000000
 

Sample Input
110 861017
 

Sample Output
593846
 

Source
2009 Asia Wuhan Regional Contest Online
想法:
n>m时,比m大的数乘起后对取余m后没影响
代码:
#include<stdio.h>
#include<string.h>
int main()
{
    int i,j,n,m,cas,t;
    long long mid,sum;
    char s[1000];
    scanf("%d",&cas);
    while(cas--)
    {
    scanf("%s %d",&s,&m);
    if(strlen(s)>=7)
    t=m;
    else sscanf(s,"%d",&t);
    mid=1;
    sum=1;
    for(i=1;i<=t;i++)
    {
    mid=(mid*i)%m;
    sum=(sum+mid)%m;
    }
    printf("%lld\n",sum%m);//这里一定一定要%m 否则会错
    }
    return 0;
}
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