hdu 1016 Prime Ring Problem

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简单的搜索题，随便看了下人家的代码之后，一次AC，哈哈哈

/* THE PROGRAM IS MADE BY PYY *//*----------------------------------------------------------------------------//Copyright (c) 2011 panyanyany All rights reserved.URL   : http://acm.hdu.edu.cn/showproblem.php?pid=1016Name  : 1016 Prime Ring ProblemDate  : Wednesday, August 10, 2011Time Stage : 2 hours lessResult:43786512011-08-10 16:13:31Accepted1016171MS204K1390 BC++pyyTest Data: Review://----------------------------------------------------------------------------*/#include <stdio.h>#include <string.h>#define MAXSIZE 40int n, len, tcase ;int prime[MAXSIZE], ans[MAXSIZE], used[MAXSIZE] ;void dfs (int a){ans[len++] = a ;used[a] = 1 ;int i ;if (len - 1 == n){if (prime[ans[1]+a]){for (i = 1 ; i < n ; ++i){printf ("%d ", ans[i]) ;}printf ("%d\n", ans[i]) ;}}else{for (i = 2 ; i <= n ; ++i){if (prime[i + a] && !used[i]){dfs (i) ;}}}--len ;used[a] = 0 ;}int main (){int i, j ;memset (prime, 1, sizeof (prime)) ;for (i = 2 ; i < MAXSIZE ; ++i){if (prime[i])for (j = i ; j*i < MAXSIZE ; ++j)prime[j*i] = 0 ;}tcase = 0 ;while (scanf ("%d", &n) != EOF){memset (used, 0, sizeof (used)) ;len = 1 ;++tcase ;printf ("Case %d:\n", tcase) ;dfs (1) ;puts ("") ;}return 0 ;}