#include <bits/stdc++.h>
#include "dreaming.h"
#define ll long long
#define pii pair<int, int>
#define st first
#define nd second
using namespace std;
vector<pii> adj[100010];
vector<int> connect;
bool visited[100010];
int max_dis, min_dis;
int u, v, node;
void dfs(int i, int prt, int dis) {
visited[i] = 1;
if (dis > max_dis) {
u = i;
max_dis = dis;
}
for (auto j : adj[i]) {
if (j.st == prt) continue;
dfs(j.st, i, dis + j.nd);
}
}
int dfs2(int i, int prt, int dis) {
if (i == v) {
min_dis = dis;
return 0;
}
for (auto j : adj[i]) {
if (j.st == prt) continue;
int k = dfs2(j.st, i, dis + j.nd);
if (k == -1) continue;
k += j.nd;
if (max(dis, k) < min_dis) {
node = i;
min_dis = max(dis, k);
}
return k;
}
return -1;
}
int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
for (int i = 0; i < M; ++i) {
adj[A[i]].push_back({B[i], T[i]});
adj[B[i]].push_back({A[i], T[i]});
}
int mx = INT_MIN, max_node;
for (int i = 0; i < N; ++i) {
if (visited[i]) continue;
max_dis = 0, u = i;
dfs(i, -1, 0);
max_dis = 0, v = u;
dfs(v, -1, 0);
min_dis = INT_MAX, node = u;
dfs2(u, -1, 0);
if (mx < max_dis) {
mx = max_dis;
max_node = node;
}
connect.push_back(node);
}
for (int i = 0; i < connect.size(); ++i) {
if (connect[i] == max_node) continue;
adj[max_node].push_back({connect[i], L});
adj[connect[i]].push_back({max_node, L});
}
max_dis = 0, u = 0;
dfs(0, -1, 0);
max_dis = 0;
dfs(u, -1, 0);
return max_dis;
}
