HDU 1016-Prime Ring Problem（DFS），hdu1016-prime

HDU 1016-Prime Ring Problem（DFS），hdu1016-prime
Prime Ring ProblemTime Limit: 4000/2000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 27595    Accepted Submission(s): 12271


Problem DescriptionA 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.


 
Inputn (0 < n < 20).
 
OutputThe 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

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要求按字典序輸出素數環。。DFS爆搜，不用剪枝。。一開始用 next_permutation()函數純暴力判結果TLE了。。
#include <cstdio>#include <iostream>#include <algorithm>#include <cstring>#include <cctype>#include <cmath>#include <cstdlib>#include <vector>#include <queue>#include <set>#include <map>#include <list>#define L long longusing namespace std;const int INF=0x3f3f3f3f;const int maxn=32;bool pri[100],vis[100];int a[35],n;void init(){memset(pri,1,sizeof(pri));pri[0]=0;pri[1]=0;for(int i=2;i<=100;i++){if(pri[i]){for(int j=2;j*i<=100;j++)pri[j*i]=0;}}}void dfs(int cur){if(cur==n&&pri[a[n-1]+a[0]]){printf("%d",a[0]);for(int i=1;i<n;i++)printf(" %d",a[i]);puts("");return ;}else{for(int i=2;i<=n;i++){if(!vis[i]&&pri[i+a[cur-1]]){a[cur]=i;vis[i]=1;dfs(cur+1);vis[i]=0;}}}}int main(){init();int cas=1;a[0]=1;while(scanf("%d",&n)!=EOF){memset(vis,0,sizeof(vis));printf("Case %d:\n",cas++);vis[1]=1;dfs(1);puts("");}return 0;}

本人是學習noip的高中生，簡單易懂的c++語言廣，深搜代碼

HDU1016：Prime Ring Problem(素數環)
題目連結：acm.hdu.edu.cn/showproblem.php?pid=1016
AC代碼：
#include<stdio.h>#include<math.h>void dfs(int x,int dep);int isprime(int m);int n,a[25],b[25];int main(){ int i,j=0; b[1]=1; while(scanf("%d",&n)!=EOF) { for(i=1;i<=24;i++) a[i]=0; j++; printf("Case %d:\n",j); if(n==1) printf("1\n"); else dfs(1,2); printf("\n"); } return 0;}void dfs(int x,int dep){ int i; if(dep==n) { for(i=2;i<=n;i++) if(a[i]==0&&isprime(i+1)&&isprime(x+i)) { b[n]=i; for(i=1;i<n;i++) printf("%d ",b[i]); printf("%d\n",b[n]); return; } } for(i=2;i<=n;i++) if(a[i]==0&&isprime(x+i)) { a[i]=1; b[dep]=i; dfs(i,dep+1); a[i]=0; } }int isprime(int m){ int i; for(i=2;i<=(int)sqrt(m);i++) if(m%i==0) return 0; return 1;}


 
杭電acm1016（找不到錯誤）

這難道不能AC嗎？