#include <bits/stdc++.h> using namespace std; using ll = long long; using PI = pair<int,int>; using PLI = pair<int,ll>; int travelTime(int n, int m, int L, int A[], int B[], int T[]) { vector<vector<PI>> g(n); for (int i = 0; i < m; ++i) { g[A[i]].push_back({B[i], T[i]}); g[B[i]].push_back({A[i], T[i]}); } vector<char> seen(n, 0); vector<ll> radii; // radius for each component ll globalMaxDiameter = 0; auto farthest_and_dist = [&](int start, const vector<int>& comp_nodes) { // iterative stack DFS to compute dist from start to all nodes in this component vector<ll> dist(n, -1); vector<int> st; st.reserve(comp_nodes.size()); st.push_back(start); dist[start] = 0; for (size_t idx = 0; idx < st.size(); ++idx) { int u = st[idx]; for (auto [v, w] : g[u]) { if (dist[v] == -1) { dist[v] = dist[u] + (ll)w; st.push_back(v); } } } // find farthest among comp_nodes int far = start; ll farD = 0; for (int u : comp_nodes) { if (dist[u] > farD) { farD = dist[u]; far = u; } } return tuple<int,ll,vector<ll>>(far, farD, move(dist)); }; // find connected components for (int i = 0; i < n; ++i) { if (seen[i]) continue; // collect component nodes via iterative DFS vector<int> comp; stack<int> st; st.push(i); seen[i] = 1; while (!st.empty()) { int u = st.top(); st.pop(); comp.push_back(u); for (auto [v, w] : g[u]) if (!seen[v]) { seen[v] = 1; st.push(v); } } // if single-node component if (comp.size() == 1) { radii.push_back(0); globalMaxDiameter = max(globalMaxDiameter, 0LL); continue; } // 1) find one diameter endpoint A auto [Aend, d1, distA] = farthest_and_dist(comp[0], comp); // 2) from Aend find Bend and distances distFromAend (already got distA if start==Aend) auto [Bend, diameter, distFromA] = farthest_and_dist(Aend, comp); globalMaxDiameter = max(globalMaxDiameter, diameter); // 3) from Bend distances int tmpStart = Bend; auto [_, dtmp, distFromB] = farthest_and_dist(tmpStart, comp); // 4) component radius = min over nodes of max(distFromA[node], distFromB[node]) ll radius = (ll)4e18; for (int u : comp) { ll mx = max(distFromA[u], distFromB[u]); if (mx < radius) radius = mx; } radii.push_back(radius); } // if only one component int k = (int)radii.size(); if (k == 1) return (int)globalMaxDiameter; sort(radii.begin(), radii.end(), greater<ll>()); // r1 >= r2 >= ... ll ans = globalMaxDiameter; // connect two largest ans = max(ans, radii[0] + radii[1] + L); if (k >= 3) ans = max(ans, radii[1] + radii[2] + 2LL * L); return (int)ans; }

/usr/bin/ld: /tmp/ccngXlCe.o: in function `main':
grader.c:(.text.startup+0xc5): undefined reference to `travelTime'
collect2: error: ld returned 1 exit status