1107. Social Clusters (30)-PAT甲级真题(并查集)

When register on a social network, you are always asked to specify your hobbies in order to find some potential friends with the same hobbies. A “social cluster” is a set of people who have some of their hobbies in common. You are supposed to find all the clusters.
Input Specification:
Each input file contains one test case. For each test case, the first line contains a positive integer N (<=1000), the total number of people in a social network. Hence the people are numbered from 1 to N. Then N lines follow, each gives the hobby list of a person in the format:
Ki: hi[1] hi[2] … hi[Ki]
where Ki (>0) is the number of hobbies, and hi[j] is the index of the j-th hobby, which is an integer in [1, 1000].
Output Specification:
For each case, print in one line the total number of clusters in the network. Then in the second line, print the numbers of people in the clusters in non-increasing order. The numbers must be separated by exactly one space, and there must be no extra space at the end of the line.
Sample Input:
8
3: 2 7 10
1: 4
2: 5 3
1: 4
1: 3
1: 4
4: 6 8 1 5
1: 4
Sample Output:
3
4 3 1

题目大意:有n个人,每个人喜欢k个活动,如果两个人有任意一个活动相同,就称为他们处于同一个社交网络。求这n个人一共形成了多少个社交网络。
分析:并查集。先写好init、findFather、Union。
0. 每个社交圈的结点号是人的编号,而不是课程。课程是用来判断是否处在一个社交圈的。
1. course[t]表示任意一个喜欢t活动的人的编号。如果当前的课程t,之前并没有人喜欢过,那么就course[t] = i,i为它自己的编号,表示i为喜欢course[t]的一个人的编号
2. course[t]是喜欢t活动的人的编号,那么findFather(course[t])就是喜欢这个活动的人所处的社交圈子的根结点,合并根结点和当前人的编号的结点i。即Union(i, findFather(course[t])),把它们处在同一个社交圈子里面
3. isRoot[i]表示编号i的人是不是它自己社交圈子的根结点,如果等于0表示不是根结点,如果不等于0,每次标记isRoot[findFather(i)]++,那么isRoot保存的就是如果当前是根结点,那么这个社交圈里面的总人数
4. isRoot中不为0的编号的个数cnt就是社交圈圈子的个数
5. 把isRoot从大到小排列,输出前cnt个,就是社交圈人数的从大到小的输出顺序