关闭农场(Closing the Farm G) 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>
using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n, m;
    if (!(cin >> n >> m)) return 0;
    vector<vector<int>> adj(n + 1);
    for (int i = 0; i < m; ++i) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    vector<int> ord(n);
    for (int i = 0; i < n; ++i) cin >> ord[i];
    vector<int> p(n + 1);
    vector<char> open(n + 1, 0), ans(n, 0);
    iota(p.begin(), p.end(), 0);
    auto find = [&](int x) {
        while (p[x] != x) x = p[x] = p[p[x]];
        return x;
    };
    int comps = 0;
    for (int i = n - 1; i >= 0; --i) {
        int u = ord[i];
        open[u] = 1;
        ++comps;
        for (int v : adj[u]) {
            if (open[v]) {
                int ru = find(u), rv = find(v);
                if (ru != rv) {
                    p[ru] = rv;
                    --comps;
                }
            }
        }
        ans[i] = (comps == 1) ? 1 : 0;
    }
    for (int i = 0; i < n; ++i) {
        cout << (ans[i] ? "YES\n" : "NO\n");
    }
    return 0;
}