Following Orders（拓扑+dfs）

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const int maxn = 25;
 5 const int inf = 0x3f3f3f3f;
 6 const int mod = 998244353;
 7 #define rep(i,first,second) for(ll i=first;i<=second;i++)
 8 #define dep(i,first,second) for(ll i=first;i>=second;i--)
 9 
10 bool g[maxn][maxn];
11 char str[maxn],ans[maxn];
12 int indegree[maxn];
13 int res;
14 
15 map<char,int>num;
16 
17 void toposort_dfs(int depth){
18     if( depth==res ){
19         printf("%s\n",ans);
20         return ;
21     }
22     rep(u,0,res-1){
23         if( indegree[u]==0 ){
24             indegree[u]--;
25             ans[depth]=str[u];
26 
27             rep(v,0,res-1){
28                 if( g[u][v] ){
29                     indegree[v]--;
30                 }
31             }
32 
33             toposort_dfs(depth+1);
34 
35             indegree[u]++;
36             rep(v,0,res){
37                 if( g[u][v] ){
38                     indegree[v]++;
39                 }
40             }
41         }
42     }
43 }
44 
45 int main()
46 {
47     char temp[55];
48     bool first=true;
49     while( gets(temp) ){
50         memset(g,false,sizeof(g));
51         memset(indegree,0,sizeof(indegree));
52 
53         int len=strlen(temp);
54         res=0;
55         rep(i,0,len-1){
56             if( isalpha(temp[i]) ) str[res++]=temp[i];
57         }
58         sort(str,str+res);
59         rep(i,0,res-1) num[str[i]]=i;
60         gets(temp);
61         len = strlen(temp);
62         int flag=0;
63         int c1,c2;
64         rep(i,0,len-1){
65             if( isalpha(temp[i])){
66                 if(flag==0){
67                     c1=num[temp[i]];
68                     flag=1;
69                 }
70                 else{
71                     c2=num[temp[i]];
72                     g[c1][c2]=true;
73                     indegree[c2]++;
74                     flag=0;
75                 }
76             }
77         }
78         memset(ans,0,sizeof(ans));
79         if( first==false ) printf("\n");
80         else first=false;
81         toposort_dfs(0);
82     }
83     return 0;
84 }