UVa 124 - Following Orders

　　题目大意：给一个变量列表和变量的大小关系，输出所有的满足约束的序列。

　　构建为有向图，然后就是拓扑排序，使用回溯输出所有的结果。

 #include <cstdio>
 #include <cstring>
 #include <cctype>
 #include <map>
 #include <algorithm>
 #include <vector>
 using namespace std;
 #define N 26
 
 map<char, int> id;
 map<int, char> var;
 vector<int> AdjList[N], ans;
 int n, indegree[];
 
 void newNode(char c)
 {
     if (!id.count(c))
     {
         int t = id.size();
         id[c] = t;
         var[t] = c;
     }
 }
 
 void dfs(int cur)
 {
     if (cur == n)
     {
         for (int i = ; i < n; i++)  printf("%c", var[ans[i]]);
         printf("\n");
         return;
     }
     for (int i = ; i < n; i++)
         if (indegree[i] == )
         {
             indegree[i] = -;
             ans.push_back(i);
             vector<int> vt;
             for (int j = ; j < AdjList[i].size(); j++)
             {
                 int v = AdjList[i][j];
                 vt.push_back(v);
                 indegree[v]--;
             }
             dfs(cur+);
             for (int j = ; j < vt.size(); j++)
                 indegree[vt[j]]++;
             ans.pop_back();
             indegree[i] = ;
         }
 }
 
 int main()
 {
 #ifdef LOCAL
     freopen("in", "r", stdin);
     freopen("out", "w", stdout);
 #endif
     char str[];
     bool first = true;
     while (gets(str))
     {
         int len = strlen(str);
         id.clear();
         var.clear();
         vector<char> varList;
         for (int i = ; i < len; i++)
             if (islower(str[i]))
                 varList.push_back(str[i]);
         sort(varList.begin(), varList.end());
         for (int i = ; i < varList.size(); i++)  newNode(varList[i]);
         n = id.size();
         gets(str);
         len = strlen(str);
         vector<int> rel;
         for (int i = ; i < len; i++)
             if (islower(str[i]))
                 rel.push_back(id[str[i]]);
         for (int i = ; i < N; i++)  indegree[i] = ;
         for (int i = ; i < N; i++)  AdjList[i].clear();
         for (int i = ; i+ < rel.size(); i += )
         {
             AdjList[rel[i]].push_back(rel[i+]);
             indegree[rel[i+]]++;
         }
         if (first)  first = false;
         else  printf("\n");
         dfs();
     }
     return ;
 }

　　第一次忘了给变量列表排序，结果WA了一次...