C :

#include <stdio.h>
#include <stdlib.h>
#define N 1010

int f[N], a[N][N], c[N];

int find(int v){
if(f[v] == v)return v;
int F = find(f[v]);
f[v] = F;
return F;
}

int main()
{
    int n;
    while(scanf("%d",&n) != EOF){
        for(int i = 1;i <= n; i++){
            f[i] = i;
            c[i] = 1;
        }
        for(int i = 1;i <= n; i++){
            scanf("%d",&a[i][0]);
            for(int j = 1;j <= a[i][0]; j++){
                scanf("%d",&a[i][j]);
            }
        }
        for(int i = n;i >= 1; i--){
            for(int j = 1;j <= a[i][0]; j++){
                if(a[i][j]>i){
                    int r1 = find(i);
                    int r2 = find(a[i][j]);
                    if(r1 != r2){
                        f[r2] = r1;
                        c[r1] += c[r2];
                        if(c[r1]>(n>>1)){
                            printf("%d\n",i);
                            return 0;
                        }
                    }
                }
            }
        }
    }
    return 0;
}

C++ :

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int f[1001],n,a[1001][1001],count[10001];
void init();
int find(int);
void work();
int main()
{
	//freopen("black0.in","r",stdin);
	init();
	work();
	return 0;
}
void init()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		count[i]=1;
		f[i]=i;
	}
	memset(a,0,sizeof(a));
	for(int i=1;i<=n;i++)
	{
		cin>>a[i][0];
		for(int j=1;j<=a[i][0];j++) cin>>a[i][j];		
	}
}
void work()
{
	for(int i=n;i>0;i--)
	{
		for(int j=1;j<=a[i][0];j++)
		{
			if(a[i][j]>i)
			{
				int x,y;
				x=find(i);
				y=find(a[i][j]);
				if(x!=y)
				{
					f[y]=x;
					count[x]+=count[y];	
					if(count[x]>(n+1)/2)
					{
						cout<<i<<endl;
						return;
					}
				}
				
			}			
		}		
	}
}
int find(int x)
{
	if(f[x]==x) return x;
	f[x]=find(f[x]);
	return f[x];
}