[HDU

基础并查集，统计有多少个根节点即可。我这里用set

#include <bits/stdc++.h>

using namespace std;
int fa[10000];
int Find(int x)
{
    if (x == fa[x])
        return x;
    return fa[x] = Find(fa[x]);
}
void Union(int x, int y)
{

    int fx = Find(x);
    int fy = Find(y);
   // printf("%d %d %d
", fa[fy], fy, fx);
    if (fx != fy)
        fa[fy] = fx;
}
int main()
{
    int t;
    while (~scanf("%d", &t))
    {
        while (t--)
        {
            fill(fa, fa + 10000, 0);
            int n, m;
            scanf("%d %d", &n, &m);
            for (int i = 1; i <= n; i++)
                fa[i] = i;
            for (int i = 1; i <= m; i++)
            {
                int a, b;
                scanf("%d %d", &a, &b);
                Union(a, b);
            }
            set<int> s;
            for (int i = 1; i <= n; i++)
                s.insert(Find(i));
            printf("%d
", s.size());
        }
    }
    return 0;
}