问题 D: 打击犯罪

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1005;//打击犯罪
int fa[maxn], mapp[maxn][maxn], danger[maxn];
void Set(int n) {
    for (int i = 1; i <= n; i++) { fa[i] = i; danger[i] = 1; }
}
int Find(int x) {
    return x == fa[x] ? x : (fa[x] = Find(fa[x]));
}
void Hebing(int x, int y) {
    fa[Find(x)] = Find(y);
    danger[y] += danger[x];
}
int Solve(int n) {
    int ans = 0;
    for (int i = n; i >= 1; i--) {
        for (int j = 1; j <= mapp[i][0]; j++)
            if (mapp[i][j] > i) {
                int r1 = Find(i), r2 = Find(mapp[i][j]);
                if (r1 != r2) {
                    fa[r2] = r1;
                    danger[r1] += danger[r2];
                    if (danger[i] > (n / 2)) {
                        return i;
                    }
                }
            }
    }
    return 0;
}
int main() {
    int n; scanf("%d", &n);
    Set(n);
    memset(mapp, 0, sizeof(mapp));
    for (int i = 1; i <= n; i++) {
        scanf("%d", &mapp[i][0]);
        for (int j = 1; j <= mapp[i][0]; j++) {
            scanf("%d", &mapp[i][j]);
        }
    }
    int ans = Solve(n);
    printf("%d\n", ans);
    return 0;
}