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 1 #include<cstdio>
 2 #include<cstring>
 3 using namespace std;
 4 const unsigned MaxJunc = 45;
 5 const unsigned MaxStreet = 1995;
 6 
 7 unsigned graph[MaxJunc][MaxStreet];
 8 unsigned stack[MaxStreet];
 9 unsigned juncDegree[MaxJunc];
10 bool hasVisited[MaxStreet];
11 unsigned top, maxStreetNo;
12 
13 void Euler(int s)
14 {
15     int i;
16     for (i = 1; i <= maxStreetNo; i++){
17         if (graph[s][i] && !hasVisited[i]){    
18             hasVisited[i] = true;
19             Euler(graph[s][i]);
20             stack[top++] = i;
21 
22         }
23     }    
24 }
25 
26 int main()
27 {
28     unsigned home;
29     unsigned x, y, z;
30     int i;
31     while (1)
32     {
33         memset(graph, 0, sizeof(unsigned)*MaxJunc*MaxStreet);
34         memset(stack, 0, sizeof(unsigned)*MaxStreet);
35         memset(juncDegree, 0, sizeof(unsigned)*MaxJunc);
36         memset(hasVisited, false, sizeof(bool)*MaxStreet);
37         maxStreetNo = 0;
38         top = 0;
39 
40         cin >> x >> y;
41         home = min(x, y);
42         if (x == 0 && y == 0)
43             break;
44         while (x != 0 && y != 0)
45         {
46             cin >> z;
47             graph[x][z] = y;
48             juncDegree[x]++;
49             graph[y][z] = x;
50             juncDegree[y]++;
51             maxStreetNo = max(maxStreetNo, z);
52             cin > x >> y;
53         }
54         for (i = 1; i < MaxJunc;++i)
55         if (juncDegree[i] % 2)
56             break;
57         if (i < MaxJunc)
58         {
59             cout << "Round trip does not exit." << endl;
60         }
61         else
62         {
63             Euler(home);
64             for (i = top - 1; i >= 0; i--)
65                 cout << stack[i] << " ";
66             cout << endl;
67         }
68     }
69     return 0;
70 }