#include <bits/stdc++.h>
#include "dreaming.h"
#define INF 0x3f3f3f3f
using namespace std;
const int MAXN = 1e5;
vector<pair<int,int>> G[MAXN];
int p[MAXN], dp1[MAXN], dp2[MAXN], node, val, dp[MAXN], best_node, best_dist;
bitset<MAXN> viz;
vector<int> nodes;
void max_self(int &a, int b) {
a = max(a, b);
}
void dfs1(int u) {
viz[u] = true;
for (auto v : G[u])
if (!viz[v.first]) {
p[v.first] = u;
dfs1(v.first);
if (dp1[u] <= dp1[v.first] + v.second) {
dp2[u] = dp1[u];
dp1[u] = dp1[v.first] + v.second;
} else max_self(dp2[u], dp1[v.first] + v.second);
}
}
void dfs2(int u, int dist) {
dp[u] = max(dp1[u], dist);
if (dp[u] < val) {
val = dp[u];
node = u;
}
for (auto v : G[u])
if (v.first != p[u]) {
if (dp1[u] == dp1[v.first] + v.second)
dfs2(v.first, max(dp2[u], dist) + v.second);
else dfs2(v.first, max(dp1[u], dist) + v.second);
}
}
void find_diameter(int u, int parent, int dist) {
if (best_dist < dist) {
best_dist = dist;
best_node = u;
}
for (auto v : G[u])
if (v.first != parent)
find_diameter(v.first, u, dist + v.second);
}
int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
for (int i = 0; i < M; ++i) {
int u = A[i], v = B[i], w = T[i];
G[u].emplace_back(v, w);
G[v].emplace_back(u, w);
}
int max_val = -1, u = -1;
for (int i = 0; i < N; ++i)
if (!viz[i]) {
p[i] = -1;
dfs1(i);
node = -1;
val = INF;
dfs2(i, 0);
nodes.emplace_back(node);
if (max_val < dp[node]) {
max_val = dp[node];
u = node;
}
}
for (int v : nodes)
if (u != v) {
G[u].emplace_back(v, L);
G[v].emplace_back(u, L);
}
best_node = best_dist = -1;
find_diameter(0, -1, 0);
best_dist = -1;
find_diameter(best_node, -1, 0);
return best_dist;
}
