HDU - 1213 How Many Tables

How Many Tables

Time Limit: 1000MS Memory Limit: 32768KB 64bit IO Format: %I64d & %I64u

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Description

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

 25 31 22 34 55 12 5 

 

Sample Output

 24 

 

Source

杭电ACM省赛集训队选拔赛之热身赛

并查集的基础题，一气呵成敲完了代码。哎，现在能够这么顺利的1Y也很少了。主要是。。。。。。题目确实很容易。代码：

#include <iostream>
#include<cstdio>
using namespace std;
const int maxn=1005;
int fa[maxn];
struct point
{
    int x,y;
}p[maxn];
int find(int x)
{
    while(x!=fa[x])
    x=fa[x];
    return x;
}
int main()
{
    int t,n,m,i,a,b;
    scanf("%d",&t);
    while(t--)
    {
        int c=0;
        scanf("%d%d",&n,&m);
        for(i=1;i<=n;i++)
        fa[i]=i;
        for(i=0;i<m;i++)
        {
           scanf("%d%d",&p[i].x,&p[i].y);
           a=find(p[i].x);
           b=find(p[i].y);
           if(a!=b)
             fa[b]=a;
        }
        for(i=1;i<=n;i++)
            if(fa[i]==i)
            c++;
        printf("%d\n",c);
    }
    return 0;
}