这里的坑不少

女生是负数，数组下标有负数，所以要先变成正数,但是直接并查集会出现男生女生重合，编号相同，所以要把女生映射到+n上，这样就完美

cpp
#include <iostream>
#include <vector>
using namespace std;

const int maxn = 500000;
int father[maxn];

int find(int x) {
    if (father[x] != x) {
        father[x] = find(father[x]);
    }
    return father[x];
}

void unionn(int x, int y) {
    int root_x = find(x);
    int root_y = find(y);
    if (root_x != root_y) {
        father[root_y] = root_x;
    }
}

int main() {
    int n, m, p, q;
    cin >> n >> m >> p >> q;

    for (int i = 1; i <= n + m; ++i) {
        father[i] = i;
    }

    for (int i = 1; i <= p; ++i) {
        int a, b;
        cin >> a >> b;
        if (find(a) != find(b)) {
            unionn(a, b);
        }
    }

    for (int i = 1; i <= q; ++i) {
        int a, b;
        cin >> a >> b;
        a *= -1;
        b *= -1;
        if (find(a + n) != find(b + n)) {
            unionn(a + n, b + n);
        }
    }

    int ansm = 0, ansf = 0;

    for (int i = 1; i <= n; ++i) {
        if (find(i) == find(1)) {
            ansm++;
        }
    }

    for (int i = n + 1; i <= n + m; ++i) {
        if (find(i) == find(n + 1)) {
            ansf++;
        }
    }

    int result = min(ansm, ansf);
    cout << result << endl;

    return 0;
}