捉迷藏(Hide and Seek S) 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 <algorithm>
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> d(n + 1, -1), q;
    q.reserve(n);
    d[1] = 0;
    q.push_back(1);
    for (size_t head = 0; head < q.size(); ++head) {
        int u = q[head];
        for (int v : adj[u]) {
            if (d[v] == -1) {
                d[v] = d[u] + 1;
                q.push_back(v);
            }
        }
    }
    int max_d = 0, best_id = 1, cnt = 0;
    for (int i = 1; i <= n; ++i) {
        if (d[i] > max_d) {
            max_d = d[i];
            best_id = i;
            cnt = 1;
        } else if (d[i] == max_d) {
            cnt++;
        }
    }
    cout << best_id << " " << max_d << " " << cnt << "\n";
    return 0;
}