HDU 1213 How Many Tables（并查集）

#include<cstdio>
#include<cstring>
using namespace std;
const int maxn = 1005;
int fa[maxn],flag[maxn];

int find(int x)
{
    int r = x;
    while (r != fa[r])    r = fa[r];
    int i = x,j;
    while (i != r)
    {
        j = fa[i];
        fa[i] = r;
        i = j;
    }
    return r;
} 

void unite(int x,int y)
{
    x = find(x),y = find(y);
    if (x != y)    fa[x] = y;
}

int main()
{
    int T;
    scanf("%d",&T);
    while (T--)
    {
        int N,M,x,y,res = 0;
        memset(flag,false,sizeof(flag));
        scanf("%d%d",&N,&M);
        for (int i = 1;i <= N;i++)    fa[i] = i;
        while (M--)
        {
            scanf("%d%d",&x,&y);
            unite(x,y);
        }
        for (int i = 1;i <= N;i++)    if (find(i) == i)    res++;
        printf("%d\n",res);
    }
    return 0;
}