NYIST OJ 题目42 一笔画问题-优快云博客

本文介绍了一种使用并查集判断无向图是否为连通图的方法，并进一步判断该连通图是否存在欧拉通路。通过输入顶点数和边数，程序能够有效地确定图中是否存在欧拉通路。

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水题。无向图欧拉通路的判定。用并查集判定是不是连通图！

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

const int maxn = 1000 + 10;
int tott[maxn];
int father[maxn];

int find(int x)
{
    if (x != father[x]) father[x] = find(father[x]);
    return father[x];
}

int main()
{
    int T;
    scanf("%d", &T);
    while (T--)
    {
        int i, n, m, u, v;
        scanf("%d%d", &n, &m);
        for (i = 0; i <= n; i++) father[i] = i;
        memset(tott, 0, sizeof(tott));
        for (i = 0; i < m; i++)
        {
            scanf("%d%d", &u, &v);
            int fu = find(u);
            int fv = find(v);
            if (fu != fv) father[fu] = fv;
            tott[u]++;
            tott[v]++;
        }
        int ji = 0, ou = 0;
        for (i = 1; i <= n; i++)
        {
            if (tott[i] == 0) continue;
            if (tott[i] % 2 == 0) ou++;
            else ji++;
        }
        int jieguo = 0;
        int th = find(1);
        for (i = 2; i <= n; i++)
        {
            int tg = find(i);
            if (tg != th) break;
        }
        if (i == n + 1) jieguo = 1;
        if (jieguo == 1)
        {
            if (ji == 0 || ji == 2) jieguo = 1;
            else jieguo = 0;
        }
        if (jieguo == 1) printf("Yes\n");
        else printf("No\n");
    }
    return 0;
}