HDoj-1016-Prime Ring Problem-DFS
Prime Ring Problem
Time Limit: 4000/2000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 27754 Accepted Submission(s): 12338
Problem Description
A ring is compose of n circles as shown in diagram. Put natural number 1, 2, ..., n into each circle separately, and the sum of numbers in two adjacent circles should be a prime.
Note: the number of first circle should 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 above process.
Print a blank line after each case.
Sample Input
6
8
Sample Output
Case 1:
1 4 3 2 5 6
1 6 5 2 3 4
Case 2:
1 2 3 8 5 6 7 4
1 2 5 8 3 4 7 6
1 4 7 6 5 8 3 2
1 6 7 4 3 8 5 2#include
#include
int n;
int prime[30]={1,1,0};
int way[30]; //存儲最後結果序列
int visit[30]; //vis表示是否訪問
void isprime() //不是素數標記為1
{
int i,j;
for(i=2;i<30;i++)
{
for(j=2*i;j<30;j+=i)
{
prime[j]=1;
}
}
}
void dfs(int temp) //環當前位置
{
int i;
if(temp==n && prime[way[0]+way[n-1]]==0)//若到達邊界且首尾兩個數字相加滿足素數
{
for(i=0;i
