Revise paste CSES_Tree_Distances_I

#include <bits/stdc++.h> // Includes all standard libraries

using namespace std;

// Using long long for integer type for larger values
#define int long long

/**
 * @brief Performs DFS to find the farthest node from a given start node.
 * @param u Current node
 * @param p Parent node
 * @param dist Distance array (dist[u] = distance from root)
 * @param adj Adjacency list
 * @param max_dist Reference to store the maximum distance found
 * @param farthest_node Reference to store the node at max_dist
 */
void find_farthest_node_dfs(int u, int p, vector<int>& dist,
                            const vector<vector<int>>& adj, int& max_dist,
                            int& farthest_node) {
    dist[u] = dist[p] + 1;
    for (int v : adj[u]) {
        if (v != p) {
            find_farthest_node_dfs(v, u, dist, adj, max_dist, farthest_node);
        }
    }
    // Check if this node is farther than the current max
    if (dist[u] > max_dist) {
        max_dist = dist[u];
        farthest_node = u;
    }
}

/**
 * @brief Performs DFS to populate distances for subtrees branching off the diameter.
 * @param u Current node
 * @param p Parent node (on the diameter)
 * @param max_dist_to_any_node The output array being populated
 * @param adj Adjacency list
 */
void populate_subtree_dists_dfs(int u, int p, vector<int>& max_dist_to_any_node,
                                const vector<vector<int>>& adj) {
    // The distance for a subtree node is its distance from the diameter
    // plus the diameter node's max distance to an endpoint.
    max_dist_to_any_node[u] = max_dist_to_any_node[p] + 1;
    for (int v : adj[u]) {
        if (v != p) {
            populate_subtree_dists_dfs(v, u, max_dist_to_any_node, adj);
        }
    }
}

signed main() {
    // Optimize C++ streams for speed
    ios::sync_with_stdio(false);
    cin.tie(NULL);

int n;
    cin >> n;

if (n == 1) {
        cout << 0 << '\n';
        return 0;
    }

vector<vector<int>> adj(n + 1);
    for (int i = 0; i < n - 1; i++) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

vector<int> dist_from_ep1(n + 1, 0);
    int max_dist = -1;
    int endpoint1 = 0;

// Use node 0 as a virtual parent with distance -1
    dist_from_ep1[0] = -1;
    
    // 1. Find one endpoint (endpoint1) of a diameter
    // We start from node 1 arbitrarily
    find_farthest_node_dfs(1, 0, dist_from_ep1, adj, max_dist, endpoint1);

// 2. Find the other endpoint (endpoint2) and the true diameter length
    // dist_from_ep1 will now store distances from endpoint1
    max_dist = -1;
    int endpoint2 = 0;
    find_farthest_node_dfs(endpoint1, 0, dist_from_ep1, adj, max_dist, endpoint2);

int diameter_len = max_dist;

// 3. Reconstruct the diameter path (from endpoint2 back to endpoint1)
    vector<int> diameter_path;
    queue<int> q;
    q.push(endpoint2);

while (!q.empty()) {
        int u = q.front();
        diameter_path.push_back(u);
        q.pop();

if (u == endpoint1) break; // Reached the other end

for (int v : adj[u]) {
            // Follow the parent pointer (dist from ep1 decreases by 1)
            if (dist_from_ep1[v] == dist_from_ep1[u] - 1) {
                q.push(v);
                break; // Found the unique parent on the path
            }
        }
    }

// 4. Calculate max distance for every node
    // This is the max distance from any node 'u' to the farthest node in the tree
    // (which will always be either endpoint1 or endpoint2).
    vector<int> max_dist_to_any_node(n + 1, 0);

// Set distances for the endpoints
    max_dist_to_any_node[endpoint1] = diameter_len;
    max_dist_to_any_node[endpoint2] = diameter_len;

int path_len = diameter_path.size();
    
    // Iterate over internal nodes of the diameter
    for (int i = 1; i < path_len - 1; i++) {
        int u_on_path = diameter_path[i];
        
        // Distance for a node on the path is its max distance to either endpoint
        int dist_to_ep1 = dist_from_ep1[u_on_path];
        int dist_to_ep2 = diameter_len - dist_to_ep1;
        max_dist_to_any_node[u_on_path] = max(dist_to_ep1, dist_to_ep2);

// 5. Run DFS for all subtrees branching off this diameter node
        for (int v_subtree : adj[u_on_path]) {
            // Avoid traversing back onto the diameter
            if (v_subtree != diameter_path[i - 1] && v_subtree != diameter_path[i + 1]) {
                populate_subtree_dists_dfs(v_subtree, u_on_path, max_dist_to_any_node, adj);
            }
        }
    }

// Print the result for all nodes
    for (int i = 1; i <= n; i++) {
        cout << max_dist_to_any_node[i] << ' ';
    }
    cout << '\n';

return 0;
}