题目：

 

1，打表的姿势不对。。。

2，不会用sprintf和atoi函数实现倒转一个数字

 

题解：

1 #include 
     
       2 #include 
      
        3 #include 
       
         4 _Bool check[1000005] = { 0 }; 5 int emirp[1005]; 6 void make_prime(void) 7 { 8     int i, j; 9     for (i = 2; i <= 500000; i++)10     {11         for (j = 2 * i; j <= 1000000; j += i)12         {13             check[j] = 1;14         }15     }16 }17 void make_Emirp(void)18 {19     int i, j;20     char string[1000];21     int count = 0;22     int p, q,temp;23     for (i = 13; count <= 1000; i++)24     {25         if (!check[i])26         {27             sprintf(string, "%d", i);28             for (p = 0, q = strlen(string) - 1; p < q; p++, q--)29             {30                 temp = string[p];31                 string[p] = string[q];32                 string[q] = temp;33             }34             int result = atoi(string);35             if (!check[result] && result != i) emirp[count++] = i;36         }37     }38 }39 int main(void)40 {41     int t;42     int k;43     scanf("%d", &t);44     make_prime();45     make_Emirp();46     while (t--)47     {48         scanf("%d", &k);49         printf("%d\n", emirp[k - 1]);50     }51     return 0;52 }