hdu--1878--欧拉回路（并查集判断连通，欧拉回路模板题）

 题目链接

 /*

     模板题-------判断欧拉回路 

     欧拉路径，无向图
     1判断是否为连通图，
     2判断奇点的个数为0
 */
 #include <iostream>
 #include <cstring>
 #include <vector>
 #include <cstdio>
 using namespace std;
 struct DisjoinSet {//并查集判断是否连通
     vector<int> father, rank;

     DisjoinSet(int n): father(n), rank(n) {
         for (int i=; i<n; i++) {
             father[i] = i;
         }
     }

     int easy_find(int v)  {//非递归
         int k, j, r;
         r = v;
         while (r!=father[r]) {
             r = father[r];
         }
         k = v;
         while (k!=r) {
             j = father[k];
             father[k] = r;
             k = j;
         }
         return r;
     }
     void merge(int x, int y) {
         int a = easy_find(x), b = easy_find(y);
         if (rank[a] < rank[b]) {
             father[a] = b;
         } else {
             father[b] = a;
             if (rank[b] == rank[a]) {
                 ++rank[a];
             }
         }
     }
 } ; 

 const int MAXN = ;
 int edge[MAXN];
 int p, q;
 int main()
 {
 //    freopen("in.txt", "r", stdin);
     while (~scanf("%d %d", &p, &q) && p) {
         memset(edge, , sizeof(edge));
         DisjoinSet mfs();
         for (int i=; i<q; i++) {
             int a, b;
             scanf("%d %d", &a, &b);
             edge[a]++;
             edge[b]++;
             mfs.merge(a, b);
         }
         int father = mfs.easy_find();
         int ct = ;
         for (int i=; i<=p; i++) {
             if (mfs.father[i] != father) {
                 ct = -;
                 break;
             }
             if (edge[i] & ) ct++;
         }
         if (ct == ) printf("1\n");//欧拉回路
         else printf("0\n");
     }
     return ;
 }