HDU 1016 Prime Ring Problem (Deep Search)

HDU 1016 Prime Ring Problem (Deep Search)
Prime Ring ProblemTime Limit: 4000/2000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission (s): 32872 Accepted Submission (s): 14544


Problem Description A ring is compose of n circles as shown in digoal. put natural number 1, 2 ,..., n into each circle separately, and the sum of numbers in two adjacent circles shoshould be a prime.

Note: the number of first circle shoshould always be 1.



Input n (0 <n <20 ).

Output The output format is shown as sample below. each row represents a series of circle numbers in the ring beginning from 1 clockwisely and anticlockwisely. the order of numbers must satisfy the above requirements. print solutions in lexicographical order.

You are to write a program that completes abve process.

Print a blank line after each case.

Sample Input

68

Sample Output

Case 1:1 4 3 2 5 61 6 5 2 3 4Case 2:1 2 3 8 5 6 7 41 2 5 8 3 4 7 61 4 7 6 5 8 3 21 6 7 4 3 8 5 2

Source Asia 1996, Shanghai (Mainland China)
Recommend JGShining | We have carefully selected several similar problems for you: 1312 1072 1242 1175




All arrays between 1-N are required to form a ring, and the sum of two adjacent numbers is required to be a prime number. Idea: because the data range of n is only 1-20, the sum of n cannot exceed 40, so the prime number within 40 is marked. Then, the DFS performs a deep search, and the direct output that matches the meaning of the question is enough. ,

Code:

#include
 
  #include#include
  
   #include
   
    #include
    
     #include
     
      using namespace std;int pv[50];int n;int p[50];int v[50];void getprime(){    for(int i=1;i<50;i++)    {        pv[i] = 1;    }    for(int i=1;i<=41;i++)    {       int pi = sqrt(i);       for(int j=2;j<=pi;j++)       {           if(i%j == 0)           {               pv[i] = 0;               break;           }       }    }}void DFS(int cnt,int x){    if(cnt == n && pv[p[n-1]+p[0]] == 1)    {        for(int i=0;i