朋友(Friends) 题解

思路分析

按题目要求使用对应数据结构与算法模拟/递推求解，注意数据范围边界与时间复杂度。

参考代码

#include <iostream>
#include <vector>
#include <numeric>
#include <algorithm>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m, P, Q;
    if (!(cin >> n >> m >> P >> Q)) return 0;
    vector<int> pa(n + 1), pb(m + 1);
    iota(pa.begin(), pa.end(), 0);
    iota(pb.begin(), pb.end(), 0);
    auto findA = [&](int x) {
        while (pa[x] != x) x = pa[x] = pa[pa[x]];
        return x;
    };
    auto findB = [&](int x) {
        while (pb[x] != x) x = pb[x] = pb[pb[x]];
        return x;
    };
    for (int i = 0; i < P; ++i) {
        int u, v;
        cin >> u >> v;
        pa[findA(u)] = findA(v);
    }
    for (int i = 0; i < Q; ++i) {
        int u, v;
        cin >> u >> v;
        u = -u;
        v = -v;
        pb[findB(u)] = findB(v);
    }
    int c1 = 0, c2 = 0;
    for (int i = 1; i <= n; ++i) if (findA(i) == findA(1)) ++c1;
    for (int i = 1; i <= m; ++i) if (findB(i) == findB(1)) ++c2;
    cout << min(c1, c2) << "\n";
    return 0;
}