hdu1878 欧拉回路--入门题

原题链接：​​http://acm.hdu.edu.cn/showproblem.php?pid=1878​​

分析：存在欧拉回路的充要：连通+度都是偶数。

并查集判连通。

#define _CRT_SECURE_NO_DEPRECATE

#include<iostream>
#include<vector>
#include<cstring>
#include<queue>
#include<stack>
#include<algorithm>
#include<cmath>
#include<string>
#include<stdio.h>
#define INF 1000000000
#define eps 0.0001
using namespace std;

int num[1005];
int n, m;
int fa[1005];

void connect(int a, int b)
{
  if (fa[a] == fa[b])
    return;
  int aa = fa[a];
  int bb = fa[b];
  for (int i = 1; i <= n; i++)
    if (fa[i] == aa)
      fa[i] = bb;
}

int main() 
{
  while (scanf("%d", &n) && n)
  {
    scanf("%d", &m);
    for (int i = 1; i <= n; i++)
    {
      fa[i] = i;
      num[i] = 0;
    }

    int a, b;
    while (m--)
    {
      scanf("%d%d", &a, &b);
      num[a]++;
      num[b]++;
      connect(a, b);
    }

    bool flag = false;
    for (int i = 1; i <= n;i++)
      if (num[i] == 0 || num[i] % 2 == 1)
      {
        flag = true;
        break;
      }

    if (flag)
      printf("0\n");
    else
    {
      int cnt = 0;
      for (int i = 1; i <= n; i++)
        if (fa[i] == i)
          cnt++;
      if (cnt == 1)
        printf("1\n");
      else
        printf("0\n");
    }
  }
  return 0;
}