最新消息:点击查看大S的省钱秘笈

POJ 2524 Ubiquitous Religions C语言版

POJ题解 Slyar 80浏览 0评论

文章作者:姜南(Slyar) 文章来源:Slyar Home (www.slyar.com) 转载请注明,谢谢合作。

依旧是并查集

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

Slyar:说下题目大意。已知有n个大学生,其中有m对宗教信仰相同的学生,请你估算这n个学生中最多有多少种宗教信仰。

依旧是简单的并查集应用。宗教信仰的最大值为学生数n,因此一开始把n个学生作为n个集合,对给出的每对大学生 a 和 b ,如果他们在不同的集合,就合并他们,然后宗教数减一。

这次依旧用到了路径压缩,只不过上一次写的是非递归,这次写了一个递归版本。也就是搜索完成回溯的时候"顺便"将当前节点的父节点直接指向祖先节点。

转载请注明:Slyar Home » POJ 2524 Ubiquitous Religions C语言版

发表我的评论
取消评论

表情

Hi,您需要填写昵称和邮箱!

  • 昵称 (必填)
  • 邮箱 (必填)
  • 网址

网友最新评论 (2)

  1. @苏洋, 不好...我没弄评论标签,不好玩...
    Slyar8年前 (2009-05-27)回复
  2. MakeSET直接放Sub Main 不好么...你的评论表情呢..消失还是没有存在过...
    苏洋8年前 (2009-05-26)回复