1 #include <stdio.h>
 2 #include <string.h>
 3 #include <stdlib.h>
 4 #include <map>
 5 #define maxn 60
 6
 7 using namespace std;
 8
 9 int indegree[ maxn ];
10 char ans[ maxn ];
11 int graph[ maxn ][ maxn ],num;
12 char str[ maxn ];
13
14 int cmp(const void *a,const void *b)
15 {
16     return (*(char *)a)-(*(char * )b);
17 }
18
19 void toposort(int depth)     //toposort+递归.
20 {
21     if(depth == num )
22     {
23         printf("%s\n",ans);
24         return;
25     }
26     for( int i = 0 ; i < num ; i++)
27     {
28         if(!indegree[ i ])
29         {
30             indegree [ i ] --;
31             ans[ depth ] = str[ i ];
32             for ( int j = 0 ; j < num ; j++ )
33                 if( graph [ i ][ j ])
34                     indegree[ j ] --;
35             toposort(depth+1);
36             indegree [ i ] ++;
37             for( int j = 0 ; j < num ; j++ )
38                 if(graph[ i ][ j ])
39                     indegree [ j ] ++;
40         }
41     }
42 }
43
44 int main()
45 {
46    // freopen("in.txt","r",stdin);
47     char inp[ maxn ];
48     while(gets( inp ))
49     {
50         memset( graph , 0 , sizeof( graph ) );
51         memset( str , 0 , sizeof( str ) );
52         memset( ans , 0 , sizeof( ans ) );
53         memset( indegree , 0 , sizeof( indegree ) );
54         map<char,int >s;
55         int len = strlen( inp ), k = 0;
56         for( int i = 0 ; i < len ; i++ )
57             if(inp[ i ] >='a' && inp[ i ] <= 'z')
58                 str[ k++ ] = inp[i];
59         qsort( str , k , sizeof( str[0] ) , cmp );
60         num = k;
61         for( int i = 0 ; i < len ; i++ )
62             s[ str[ i ] ] = i;     //对点进行构图一定要在排序之后，不然会wa.
63         memset( inp , 0 , sizeof( inp ) );
64         gets( inp );
65         len = strlen( inp );
66         for( int i = 0 ; i < len ; i += 4 )
67         {
68             graph[ s[ inp[ i ] ] ][ s[ inp[ i + 2 ] ] ] = 1;
69             indegree [ s[ inp[ i + 2 ] ] ] ++;
70         }
71         toposort(0);
72         memset( inp , 0 ,sizeof( inp ) );
73         printf("\n");
74     }
75     return 0;
76 }