Tree Properties

struct Tree {
    int n;
    vector<vector<int>> adj;
    vector<int> dist;
    Tree(int _n) {
        n = _n;
        const int inf = 1e8;
        dist.resize(n + 1, -inf);
        adj.resize(n + 1, vector<int>());
    }
    void add(int u, int v) {
        adj[u].push_back(v);
        adj[v].push_back(u);
    }
    void predfs(int node, int par, int &one_end, int &max_dist, int h) {
        if(h > max_dist) {
          max_dist = h;
          one_end = node;
        }
        for(int u: adj[node]) {
         if(u != par) {
            predfs(u, node, one_end, max_dist, h + 1);
         }
        }
    }
    pair<pair<int,int>, int> diameter() {
       int max_dist = 0;
       int one_end = -1;
       predfs(1, 0, one_end, max_dist, 0);
       int d = 0;
       int last_end = -1;
       predfs(one_end, 0, last_end, d, 0);
       return {{one_end, last_end}, d};
    }
    void dfs(int node, int par, int d) {
        dist[node] = max(dist[node], d);
        for(int u: adj[node]) {
          if(u != par) {
            dfs(u, node, d + 1);
          }
        }
    }
    void farthest_node(int node1, int node2) {
        dfs(node1, 0, 0);
        dfs(node2, 0, 0);
    }
};