hdu--1878--Eulerian circuit (and check the set to judge connectivity, Euler circuit template question)

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1  /* 
2  
3      template questions ------- judge Euler circuit 
 4       
5      Euler path, undirected graph
 6      1 judge whether it is a connected graph, 
 7      2 judge the number of singularities is 0
 8  */ 
9 # include <iostream> 
 10 #include <cstring>
 11 #include <vector>
 12 #include <cstdio>
 13  using  namespace std;
 14  struct DisjoinSet {//Check the set to determine whether it is connected
 15      vector< int > father, rank;
 16      
17      DisjoinSet( int n): father(n), rank(n) {
 18          for (int i=0; i<n; i++) {
19             father[i] = i;
20         }
21     }
22     
23     int easy_find(int v)  {//非递归 
24         int k, j, r;
25         r = v;
26         while (r!=father[r]) {
27             r = father[r];
28         }
29         k = v;
30         while (k!=r) {
31             j = father[k];
32             father[k] = r;
33             k = j;
34         }
35         return r;
36     }
37     void merge(int x, int y) {
38         int a = easy_find(x), b = easy_find(y);
39         if (rank[a] < rank[b]) {
40             father[a] = b;
41         } else {
42             father[b] = a;
43             if (rank[b] == rank[a]) {
44                 ++rank[a];
45             }
46         }
47     }
48 } ; 
49 
50 const int MAXN = 1010;
51 int edge[MAXN];
52 int p, q;
53 int main()
54 {
55 //    freopen("in.txt", "r", stdin);
56     while (~scanf("%d %d", &p, &q) && p) {
57         memset(edge, 0, sizeof(edge));
58         DisjoinSet mfs(1010);
59         for (int i=0; i<q; i++) {
60             int a, b;
61             scanf("%d %d", &a, &b);
62             edge[a]++;
63             edge[b]++;
64             mfs.merge(a, b);
65         }
66         int father = mfs.easy_find(1);
67         int ct = 0;
68         for (int i=1; i<=p; i++) {
69             if (mfs.father[i] != father) {
70                 ct = -1;
71                 break;
72             }
73             if (edge[i] & 1) ct++;
74         }
75         if (ct == 0) printf("1\n");//欧拉回路
76         else printf("0\n");
77     }
78     return 0;
79 }