【并查集】Ubiquitou Religions

DescriptionThere are so many different religions in the world today that it is difficult to keep trackof them all. You are interested in finding out how many different religions students in youruniversity believe in.You know that there are n students in your university (0 < n <= 50000). It is infeasible foryou to ask every student their religious beliefs. Furthermore, many students are not comfortableexpressing their beliefs. One way to avoid these problems is to ask m (0 <= m <= n(n-1)/2) pairsof students and ask them whether they believe in the same religion (e.g. they may know if theyboth 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 possiblyrepresented on campus. You may assume that each student subscribes to at most one religion.InputThe input consists of a number of cases. Each case starts with a line specifying the integersn and m. The next m lines each consists of two integers i and j, specifying that students iand j believe in the same religion. The students are numbered 1 to n. The end of input isspecified by a line in which n = m = 0.OutputFor each test case, print on a single line the case number (starting with 1) followed bythe maximum number of different religions that the students in the university believe in.Sample Input10 91 21 31 41 51 61 71 81 91 1010 42 34 54 85 80 0Sample OutputCase 1: 1Case 2: 7HintHuge input, scanf is recommended.

很裸的并查集，不用多说……

Accode：

#include <cstdio>#include <cstdlib>#include <algorithm>#include <string>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;}