usaco1.53Superprime Rib

预处理出前4位的超级素数，再枚举后四位

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 1 /*

 2   ID: your_id_here

 3   PROG: sprime

 4   LANG: C++

 5   */

 6 #include <iostream>

 7 #include<cstdio>

 8 #include<cstring>

 9 #include<cmath>

10 #include<algorithm>

11 using namespace std;

12 int num[10][1000],f[20],g,n,k[10],nn[10000],kk;

13 int prime(int x)

14 {

15     if(x==1)

16     return 0;



17     int k = sqrt(x),i,flag = 1;

18     for(i = 2 ;i <= k  ;i++)

19     if(x%i==0)

20     {

21         flag  =0;

22         break;

23     }

24     return flag;

25 }

26 void dfs(int x , int v)

27 {

28     int y = x,i;

29     if(!prime(x))

30     return ;

31     if(v==n)

32     {

33         if(prime(x))

34         {

35             kk++;

36             nn[kk] = x;

37         }

38         return ;

39     }

40     for(i = 0 ; i <= 9 ; i++)

41     {

42         x = x*10+i;

43         dfs(x,v+1);

44         x = y;

45     }

46 }

47 int main()

48 {

49     freopen("sprime.in","r",stdin);

50     freopen("sprime.out","w",stdout);

51     int i,j;

52     cin>>n;

53     num[1][0] = 2;

54     g = 0;

55     for(i = 3; i <= 9 ; i++)

56     if(prime(i))

57     num[1][++g] = i;

58     k[1] = g;

59     g = -1;



60     for(i = 11 ; i <= 99 ; i++)

61     {

62         if(prime(i/10)&&prime(i))

63         num[2][++g] = i;

64     }

65     k[2] = g;

66     g = -1;

67     for(i = 101 ; i <= 999 ; i++)

68     {

69         if(prime(i/10)&&prime(i)&&prime(i/100))

70         num[3][++g] = i;

71     }

72     k[3] = g;

73     g = -1;

74     for(i = 1001 ; i <= 9999 ; i++)

75     {

76         if(prime(i/10)&&prime(i)&&prime(i/100)&&prime(i/1000))

77         num[4][++g] = i;

78     }

79     k[4] = g;

80     if(n<=4)

81     {

82         for(i = 0 ; i <= k[n] ; i++)

83         cout<<num[n][i]<<endl;

84     }

85     else

86     {

87         for(i = 0 ; i <= k[4] ; i++)

88         {

89             dfs(num[4][i],4);

90         }

91         sort(nn+1,nn+kk+1);

92         for(i = 1;  i <= kk ; i++)

93         cout<<nn[i]<<endl;

94     }

95     fclose(stdin);

96     fclose(stdout);

97     return 0;

98 }