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=0; 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 = 1010;
int edge[MAXN];
int p, q;
int main()
{
//    freopen("in.txt", "r", stdin);
    while (~scanf("%d %d", &p, &q) && p) {
        memset(edge, 0, sizeof(edge));
        DisjoinSet mfs(1010);
        for (int i=0; i<q; i++) {
            int a, b;
            scanf("%d %d", &a, &b);
            edge[a]++;
            edge[b]++;
            mfs.merge(a, b);
        }
        int father = mfs.easy_find(1);
        int ct = 0;
        for (int i=1; i<=p; i++) {
            if (mfs.father[i] != father) {
                ct = -1;
                break;
            }
            if (edge[i] & 1) ct++;
        }
        if (ct == 0) printf("1
");//欧拉回路
        else printf("0
");
    }
    return 0;
}