杭電1016（dfs）增所廣收
阿新 • • 發佈：2019-01-22
</pre><div class="panel_content" style="height: auto; margin: 0px; padding: 0px 20px; font-size: 14px; font-family: 'Times New Roman'; background: url("panel-content.png") repeat-y;">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.<img src="http://acm.hdu.edu.cn/data/images/1016-1.gif" style="border: none; max-width: 100%;" alt="" /></div><div class="panel_bottom" style="height: auto; margin: 0px; font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center; background: url("panel-bottom.png") 0% 0% no-repeat;"> </div><br style="font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center;" /><div class="panel_title" align="left" style="height: 38px; padding: 0px 14px; color: rgb(124, 169, 237); font-size: 18px; font-family: Arial; font-weight: bold; background: url("panel-title.png") 0% 100% no-repeat transparent;">Input</div><div class="panel_content" style="height: auto; margin: 0px; padding: 0px 20px; font-size: 14px; font-family: 'Times New Roman'; background: url("panel-content.png") repeat-y;">n (0 < n < 20).</div><div class="panel_bottom" style="height: auto; margin: 0px; font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center; background: url("panel-bottom.png") 0% 0% no-repeat;"> </div><br style="font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center;" /><div class="panel_title" align="left" style="height: 38px; padding: 0px 14px; color: rgb(124, 169, 237); font-size: 18px; font-family: Arial; font-weight: bold; background: url("panel-title.png") 0% 100% no-repeat transparent;">Output</div><div class="panel_content" style="height: auto; margin: 0px; padding: 0px 20px; font-size: 14px; font-family: 'Times New Roman'; background: url("panel-content.png") repeat-y;">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.</div><div class="panel_bottom" style="height: auto; margin: 0px; font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center; background: url("panel-bottom.png") 0% 0% no-repeat;"> </div><br style="font-family: 'Times New Roman';font-size:14px; text-align: -webkit-center;" /><div class="panel_title" align="left" style="height: 38px; padding: 0px 14px; color: rgb(124, 169, 237); font-size: 18px; font-family: Arial; font-weight: bold; background: url("panel-title.png") 0% 100% no-repeat transparent;">Sample Input</div><div class="panel_content" style="height: auto; margin: 0px; padding: 0px 20px; font-size: 14px; font-family: 'Times New Roman'; background: url("panel-content.png") repeat-y;"><pre style="word-wrap: break-word; white-space: pre-wrap; margin-top: 0px; margin-bottom: 0px;"><div style="font-family: 'Courier New', Courier, monospace;">6 8</div>
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 一個環，相鄰兩個數之和是素數，，並且把所以可能都按順序輸出來。
#include <iostream> #include <math.h> using namespace std; #define max 21 int vis[max],hk[max]; int n,k=1; bool ls(int a,int b) { int c=a+b; for(int i=2;i*i<=c;i++) { if(c%i==0) return false; } return true; } void DFS(int a) { if(n==a&&ls(1,hk[n-1])) { cout<<hk[0]; int i; for(i=1;i<n;i++) { cout<<' '<<hk[i]; } cout<<endl; } else { int i; for(i=2;i<=n;i++) { if(vis[i]==true||!ls(hk[a-1],i)) { continue; } hk[a]=i; vis[i]=true; DFS(a+1); vis[i]=false; } } } int main() { hk[0]=1; memset(vis,false,sizeof(vis)); while(cin>>n) { cout<<"Case "<<k++<<':'<<endl; DFS(1); cout<<endl; } return 0; }