class Solution {

vector<vector<int>>adj;

int V;

public:

int treeDiameter(vector<vector<int>>& edges)

{

V = edges.size()+1;

adj.resize(V);

for (auto edge:edges)

{

adj[edge[0]].push_back(edge[1]);

adj[edge[1]].push_back(edge[0]);

}

auto t1 = bfs(0);

auto t2 = bfs(t1.first);

return t2.second;

}

pair<int, int> bfs(int u)

{

vector<int>dis(V, -1);

queue<int> q;

q.push(u);

dis[u] = 0;

while (!q.empty())

{

int t = q.front();

q.pop();

for (auto it = adj[t].begin(); it != adj[t].end(); it++)

{

int v = *it;

if (dis[v] == -1)

{

q.push(v);

dis[v] = dis[t] + 1;

}

}

}

int maxDis = 0;

int nodeIdx;

for (int i = 0; i < V; i++)

{

if (dis[i] > maxDis)

{

maxDis = dis[i];

nodeIdx = i;

}

}

return make_pair(nodeIdx, maxDis);

}

};