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- #include <iostream>
- #include <vector>
- #include <queue>
- using namespace std;
- const int maxn=500000;
- vector<int> graph[maxn];
- pair<int, int> bfs(int S) {
- queue<int> q;
- q.push(S);
- q.push(0);
- vector<bool> visited(maxn, false);
- visited[S] = true;
- int max_dist = 0;
- int furthest_node = -1;
- while(!q.empty()) {
- int node = q.front();
- q.pop();
- int dist = q.front();
- q.pop();
- if(max_dist < dist) {
- max_dist = dist;
- furthest_node = node;
- }
- for(int i = 0; i < (int) graph[node].size(); i++) {
- int neighbour = graph[node][i];
- if(!visited[neighbour]) {
- visited[neighbour] = true;
- q.push(neighbour);
- q.push(dist + 1);
- }
- }
- }
- return make_pair(furthest_node, max_dist);
- }
- int main() {
- int n;
- cin >> n;
- if(n == 1) {
- cout << 0 << endl;
- return 0;
- }
- for(int i = 1; i < n; i++) {
- int a, b;
- cin >> a >> b;
- a--; b--;
- graph[a].push_back(b);
- graph[b].push_back(a);
- }
- int farthest_node_from_node_0 = bfs(0).first;
- int res = bfs(farthest_node_from_node_0).second;
- cout << res << endl;
- return 0;
- }
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