POJ 1041 John's trip

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 2010;
18 int g[50][maxn],degree[50],stk[maxn],tp,n,m;
19 bool vis[maxn];
20 void dfs(int u) {
21     for(int i = 1; i <= n; i++) {
22         if(!vis[i] && g[u][i]) {
23             vis[i] = true;
24             dfs(g[u][i]);
25             stk[tp++] = i;
26         }
27     }
28 }
29 int main() {
30     int x,y,z,st,i;
31     while(scanf("%d %d",&x,&y),x||y) {
32         n = m = tp = 0;
33         memset(vis,false,sizeof(vis));
34         memset(degree,0,sizeof(degree));
35         memset(g,0,sizeof(g));
36         st = min(x,y);
37         scanf("%d",&z);
38         n = max(n,z);
39         m = max(m,max(x,y));
40         g[x][z] = y;
41         g[y][z] = x;
42         degree[x]++;
43         degree[y]++;
44         while(scanf("%d %d",&x,&y),x||y) {
45             scanf("%d",&z);
46             n = max(n,z);
47             m = max(m,max(x,y));
48             g[x][z] = y;
49             g[y][z] = x;
50             degree[x]++;
51             degree[y]++;
52         }
53         for(i = 1; i <= m; i++)
54             if(degree[i]&1) break;
55         if(i <= m) puts("Round trip does not exist.");
56         else {
57             dfs(st);
58             tp--;
59             printf("%d",stk[tp--]);
60             while(tp >= 0) printf(" %d",stk[tp--]);
61             puts("");
62         }
63     }
64     return 0;
65 }
66 /*
67 1 2 1
68 2 3 2
69 3 1 6
70 1 2 5
71 2 3 3
72 3 1 4
73 0 0
74 */