usaco-3.2-fact4-pass

这个是数论知识，列举一下前面十几个就可以看出规律：

/*
ID: qq104801
LANG: C++
TASK: fact4
*/

#include <iostream>
#include <fstream>
#include <cstring>
#include <vector>
#include <map>
#include <list>
#include <set>
#include <queue>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;

void test()
{    
    freopen("fact4.in","r",stdin);
    freopen("fact4.out","w",stdout);
    int n;
    cin>>n;
    int m=1,pp=100000,f;
    for(int i=1;i<=n;i++)
    {
        f=i%pp;
        m*=f;
        while(m%10==0)
            m/=10;
        while(m/pp>0)
            m%=pp;
    }
    cout<<m%10<<endl; 
}

int main () 
{        
    test();        
    return 0;
}

test data:

USACO Training
Grader Results     
8 users online
CHN/2 DNK/1 GRC/1 IND/1 SGP/1 TUR/1 USA/1

USER: cn tom [qq104801]
TASK: fact4
LANG: C++

Compiling...
Compile: OK

Executing...
   Test 1: TEST OK [0.005 secs, 3372 KB]
   Test 2: TEST OK [0.005 secs, 3372 KB]
   Test 3: TEST OK [0.005 secs, 3372 KB]
   Test 4: TEST OK [0.005 secs, 3372 KB]
   Test 5: TEST OK [0.008 secs, 3372 KB]
   Test 6: TEST OK [0.005 secs, 3372 KB]
   Test 7: TEST OK [0.011 secs, 3372 KB]
   Test 8: TEST OK [0.008 secs, 3372 KB]
   Test 9: TEST OK [0.008 secs, 3372 KB]
   Test 10: TEST OK [0.008 secs, 3372 KB]

All tests OK.

YOUR PROGRAM ('fact4') WORKED FIRST TIME! That's fantastic -- and a rare thing. Please accept these special automated congratulations.

Here are the test data inputs:

------- test 1 ----
1
------- test 2 ----
2
------- test 3 ----
7
------- test 4 ----
14
------- test 5 ----
143
------- test 6 ----
645
------- test 7 ----
777
------- test 8 ----
888
------- test 9 ----
999
------- test 10 ----
1000

Keep up the good work!
Thanks for your submission!