UVA 10054 (欧拉回路) The Necklace

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<iostream>
 4 #include<algorithm>
 5 #include<vector>
 6 using namespace std;
 7 
 8 const int M = 1e3 + 10;
 9 int cas,head[M*4],father[60],du[60];
10 int vis[60][60];
11 
12 struct Edge{
13    int next,to;
14 }edge[M*4];
15 
16 int findest(int x)
17 {
18     if (x==father[x]) return x;
19     father[x]=findest(father[x]);
20     return father[x];
21 }
22 
23 void add(int v,int u)
24 {
25     edge[++cas].next=head[v];
26     edge[cas].to=u;
27     head[v]=cas;
28 }
29 
30 void euler(int u)
31 {
32     for (int i=head[u] ; i ; i=edge[i].next){
33         int v=edge[i].to;
34         if (!vis[u][v]) continue;
35         vis[u][v]--;vis[v][u]--;
36         euler(edge[i].to);
37         printf("%d %d\n",v,u);
38     }
39 }
40 
41 int main()
42 {
43     int t,tem=0;
44     scanf("%d",&t);
45     int e=t;
46     while (t--)
47     {
48         int n,w;cas=0;
49         scanf("%d",&n);
50         memset(du,0,sizeof(du));
51         memset(vis,0,sizeof(vis));
52         memset(head,0,sizeof(head));
53         for (int i=1 ; i<=50 ; i++) father[i]=i;
54         for (int i=1 ; i<=n ; i++) {
55             int l,r;
56             scanf("%d%d",&l,&r);
57             if (i==1) w=l;
58             du[l]++;du[r]++;
59             add(l,r);
60             add(r,l);
61             vis[l][r]++;vis[r][l]++;
62             int x=findest(l),y=findest(r);
63             if (x!=y) father[x]=y;
64         }
65         bool flag=false;
66         int x=findest(w);
67         for (int i=1 ; i<=50 ; i++){
68             if (du[i]==0) continue;
69             if (du[i]%2!=0) flag=true;
70             if (findest(i)!=x) flag=true;
71             if (flag) break;
72         }
73         cas=0;
74         if (tem!=0) printf("\n");
75         printf("Case #%d\n",++tem);
76         if (flag) puts("some beads may be lost");
77         else  euler(w);
78     }
79     return 0;
80 }