杭电1856

Problem Description
Mr Wang wants some boys to help him with a project. Because the project is rather complex, the more boys come, the better it will be. Of course there are certain requirements.

Mr Wang selected a room big enough to hold the boys. The boy who are not been chosen has to leave the room immediately. There are 10000000 boys in the room numbered from 1 to 10000000 at the very beginning. After Mr Wang’s selection any two of them who are still in this room should be friends (direct or indirect), or there is only one boy left. Given all the direct friend-pairs, you should decide the best way.

Input
The first line of the input contains an integer n (0 ≤ n ≤ 100 000) - the number of direct friend-pairs. The following n lines each contains a pair of numbers A and B separated by a single space that suggests A and B are direct friends. (A ≠ B, 1 ≤ A, B ≤ 10000000)

Output
The output in one line contains exactly one integer equals to the maximum number of boys Mr Wang may keep.

Sample Input
4
1 2
3 4
5 6
1 6
4
1 2
3 4
5 6
7 8

Sample Output
4
2
此处并查集略有改变，具有能记录每棵树有几个节的功能，算法就是加了一个数组y[1000];

中心函数
for(int i=0;ii++)
{
    cin>>a>>b;
    k=find(a);
    g=find(b);
    if(k!=g)
    {
        x[g]=k;
        y[k]+=y[g];
    }
}

每次加上一个节点都把这个节点的成员加给根节点。

AC代码
#include
#include
using namespace std;
int x[10000000];
int y[10000000];
int find(int n)
{
    if(x[n]==n)
        return n;
    else
        return x[n]=find(x[n]);
}
int main()
{
    int n;
    while(cin>>n)
    {
        int a,b,k,g;
        for(int i=0; i<=10000000; i++)
        {
            x[i]=i;
            y[i]=1;
        }
        for( int i=0; icin >> a >> b;
            k = find(a);
            g = find(b);
            if( k != g )
            {
                x[g] = k;
                y[k] += y[g];
            }
        }
        int Max=0;
        for(int i=1; i<10000000; i++)
        {
            if(x[i]==i)
                if(y[i]>Max)
                    Max=y[i];
        }
        cout<