C - How Many Tables 杭电oj_____1213

How Many Tables

Today is Ignatius’ birthday. He invites a lot of friends. Now it’s dinner time. Ignatius wants to know how many tables he needs at least. You have to notice that not all the friends know each other, and all the friends do not want to stay with strangers.
One important rule for this problem is that if I tell you A knows B, and B knows C, that means A, B, C know each other, so they can stay in one table.
For example: If I tell you A knows B, B knows C, and D knows E, so A, B, C can stay in one table, and D, E have to stay in the other one. So Ignatius needs 2 tables at least.

Input

The input starts with an integer T(1<=T<=25) which indicate the number of test cases. Then T test cases follow. Each test case starts with two integers N and M(1<=N,M<=1000). N indicates the number of friends, the friends are marked from 1 to N. Then M lines follow. Each line consists of two integers A and B(A!=B), that means friend A and friend B know each other. There will be a blank line between two cases.

Output

For each test case, just output how many tables Ignatius needs at least. Do NOT print any blanks.

Sample Input

2
5 3
1 2
2 3
4 5

5 1
2 5

Sample Output

2
4

这道题是说，已知会告诉你各个独立集的关系，通过这些关系的作用之后，会留下多少个独立的集合！
根据已知条件我们可以讲有关系的集合进行合并，最后看谁的祖先是本身，就说明它将会是一个独立集！
代码：

#include<stdio.h>
#define M 1009
int p[M];
void init(int n)
{
    int i;
    for(i=1; i<=n; i++)
        p[i]=i;
}
int fond_root(int a)
{
    int i,r=a;
    while(p[r]!=r)
    {
        r=p[r];
    }
    while(a!=r)
    {
        i=p[a];
        p[a]=r;
        a=i;
    }
    return a;
}
int main()
{
    int i,j,n,m,t,k,a,b,num,f1,f2;
    scanf("%d",&t);
    for(k=1; k<=t; k++)
    {
        scanf("%d%d",&n,&m);
        init(n);
        for(i=1; i<=m; i++)
        {
            scanf("%d%d",&a,&b);
            f1=fond_root(a);
            f2=fond_root(b);
            if(f1!=f2)
                p[f1]=f2;
        }
        num=0;
        for(j=1; j<=n; j++)
        {
            if(p[j]==j)
                num++;
        }
        printf("%d\n",num);
    }
    return 0;
}

标签：Tables,Ignatius,oj,_____,f1,int,f2,num,knows
来源： https://blog.csdn.net/CHEN_XU_LING/article/details/110726070