【并查集】Ubiquitou Religions

Description
There are so many different religions in the world today that it is difficult to keep track
of them all. You are interested in finding out how many different religions students in your
university believe in.

You know that there are n students in your university (0 < n <= 50000). It is infeasible for
you to ask every student their religious beliefs. Furthermore, many students are not comfortable
expressing their beliefs. One way to avoid these problems is to ask m (0 <= m <= n(n-1)/2) pairs
of students and ask them whether they believe in the same religion (e.g. they may know if they
both attend the same church). From this data, you may not know what each person believes in,
but you can get an idea of the upper bound of how many different religions can be possibly
represented on campus. You may assume that each student subscribes to at most one religion.

Input
The input consists of a number of cases. Each case starts with a line specifying the integers
n and m. The next m lines each consists of two integers i and j, specifying that students i
and j believe in the same religion. The students are numbered 1 to n. The end of input is
specified by a line in which n = m = 0.

Output
For each test case, print on a single line the case number (starting with 1) followed by
the maximum number of different religions that the students in the university believe in.

Sample Input

10 9
1 2
1 3
1 4
1 5
1 6
1 7
1 8
1 9
1 10
10 4
2 3
4 5
4 8
5 8
0 0

Sample Output

Case 1: 1
Case 2: 7

Hint
Huge input, scanf is recommended.

很裸的并查集，不用多说……

Accode：

#include 
#include 
#include 
#include 

int F[50010];

inline int getint()
{
    int res = 0; char tmp;
    while (!isdigit(tmp = getchar()));
    do res = (res << 3) + (res << 1) + tmp - '0';
    while (isdigit(tmp = getchar()));
    return res;
}

int Find(int x)
{return F[x] == x ? x : F[x] = Find(F[x]);}

int main()
{
    freopen("Ubiquitou_Religions.in", "r", stdin);
    freopen("Ubiquitou_Religions.out", "w", stdout);
    for (int T = 1; ; ++T)
    {
        int n = getint(), m = getint();
        if (!n && !m) break;
        for (int i = 1; i < n + 1; ++i) F[i] = i;
        while (m--) F[Find(getint())] = Find(getint());
        for (int i = 1; i < n + 1; ++i) Find(i);
        std::sort(F + 1, F + n + 1);
        int ans = 1;
        for (int i = 2; i < n + 1; ++i)
            ans += F[i] != F[i - 1];
        printf("Case %d: %d\n", T, ans);
    }
    return 0;
}