hdu 1016 dfs+方案输出

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#define MAX 27

using namespace std;

int n;
int a[MAX];
bool used[MAX];
bool p[MAX];

void init ( )
{
    memset ( p , 0 , sizeof ( p ) );
    p[2] = p[3] = p[5] = p[7] = p[11] 
    = p[13] = p[17] = p[19] = p[23]
    = p[29] = p[31] = p[37] = 1;
}

void dfs ( int u = 1  , int h = 1 )
{
    a[h] = u;
    if ( h== n && !p[a[h]+a[1]] ) return;
    if ( h == n )
    {
        for ( int i = 1 ; i < n ; i++ )
            printf ( "%d " , a[i] );
        printf ( "%d\n" , a
 );
        return;
    }
    for ( int i = 1 ; i <= n ; i++ )
    {
        if ( used[i] ) continue;
        if ( !p[i+a[h]] ) continue;
        used[i] = true;
        dfs ( i , h+1 );
        used[i] = false;
    }
}

int main ( )
{
    init ();
    int c = 1;
    while ( ~scanf ( "%d" , &n ) )
    {  
        memset ( used , 0 , sizeof ( used ) ); 
        printf ( "Case %d:\n" , c++ );
        used[1] = true;
        dfs ( );
        puts ("");
    }
}