uva 10006 Carmichael Numbers

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=947

打出素数表，快速幂取模。

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <cmath>

 4 #include <algorithm>

 5 #define ll long long

 6 #define maxn 65000

 7 using namespace std;

 8 

 9 int n;

10 bool vis[maxn*10];

11 

12 

13 ll pow_mod(ll a,ll p,ll n)

14 {

15     if(p==0) return 1;

16     ll ans=pow_mod(a,p/2,n);

17     ans=ans*ans%n;

18     if(p%2==1) ans=ans*a%n;

19     return ans;

20 }

21 void Get_prime()

22 {

23     memset(vis,false,sizeof(vis));

24     int m=(int)sqrt(maxn*1.0);

25     for(int i=2; i<=m; i++)

26     {

27         if(!vis[i])

28         {

29             for(int j=i*i; j<=maxn; j+=i)

30             {

31                 vis[j]=true;

32             }

33         }

34     }

35 }

36 

37 

38 int main()

39 {

40     Get_prime();

41     while(scanf("%d",&n)!=EOF)

42     {

43         if(n==0) break;

44         if(!vis[n])

45         {

46             printf("%d is normal.\n",n);

47             continue;

48         }

49         bool flag=true;

50         for(int i=2; i<n; i++)

51         {

52             ll c=pow_mod((ll)i,(ll)n,(ll)n);

53             if(c!=i)

54             {

55                 flag=false;

56                 break;

57             }

58         }

59         if(flag)

60         {

61             printf("The number %d is a Carmichael number.\n",n);

62         }

63         else printf("%d is normal.\n",n);

64     }

65     return 0;

66 }

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