Untitled

#include <bits/stdc++.h> 
#define pii pair<int, int>
using namespace std;

struct Node_Info
{
    int height;
    int diameter;
    Node_Info(int h, int d)
    {
        this->height = h;
        this->diameter = d;
    }
};

Node_Info dfs(vector<vector<int>> &adj, int node, int parent) 
{
    // base case: node is a leaf
    if (adj[node].size() == 0) return Node_Info(0, 0);

    int max_child_height = 0, second_max_child_height = 0;
    int max_child_diam = 0;

    for (int adjNode : adj[node])
    {
        if (adjNode == parent) continue;

        Node_Info child_info = dfs(adj, adjNode, node);

        int child_height = child_info.height;
        int child_diam = child_info.diameter;

        if (child_height > max_child_height)
        {
            second_max_child_height = max_child_height;
            max_child_height = child_height;
        }
        else if (child_height > second_max_child_height)
        {
            second_max_child_height = child_height;
        }

        if (child_diam > max_child_diam)
        {
            max_child_diam = child_diam;
        }
    }

    int node_height = max_child_height + 1;
    int node_diam = max(max_child_diam, max_child_height + second_max_child_height); 

    return Node_Info(node_height, node_diam);


}

int longestPath(vector<vector<int>> &edges, int n)
{
    // Write your code here
    vector<vector<int>> adj(n);
    // create adj list
    for (vector<int> edge : edges)
    {
        int first_node = edge[0];
        int second_node = edge[1];
        adj[first_node].push_back(second_node);
        adj[second_node].push_back(first_node);
    }

    Node_Info ans = dfs(adj, 0, -1);

    return ans.diameter;

}