UVa 10608 - Friends

并查集，实际就是统计图中最大连通分支中节点的个数。

代码如下：

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>

using namespace std;
const int MAXN = 30002;
int friends[MAXN], p[MAXN];
int find(int x)
{
    return p[x] == x ? x : (p[x] =find(p[x]));
}
int main()
{
#ifdef test
    freopen("sample.txt", "r", stdin);
#endif
    int m, n, t, x, y, u, v, _max;
    scanf("%d", &t);
    while(t--)
    {
        _max = 0;
        scanf("%d%d", &n, &m);
        memset(friends, 0, (n+1)*sizeof(friends[0]));
        for(int i=1; i<=n; i++)
            p[i] = i;
        for(int i=0; i<m; i++)
        {
            scanf("%d%d", &x, &y);
            u = find(x);
            v = find(y);
            if(u != v)
                p[u] = v;
        }
        for(int i=1; i<=n; i++)
        {
            x = find(i);
            ++friends[x];
        }
        for(int i=1; i<=n; i++)
            if(friends[i] > _max)
                _max = friends[i];
        printf("%d\n", _max);
    }
    return 0;
}