#include "dreaming.h"
#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define ALL(x) x.begin(),x.end()
using namespace std;
using VI = vector <int>;
using PII = pair <int, int>;
const int N = 1e5+5;
vector <PII> paths[N];
bool vis[N];
int n, m, L, sizes[N], len;
PII dp[N];
PII getFarthest(int pos, int par = 0) {
dp[pos] = {0, pos};
for (auto [a, b] : paths[pos]) {
if (a == par) continue;
PII tmp = getFarthest(a, pos);
if (dp[pos].ff < tmp.ff + b) dp[pos] = {tmp.ff + b, tmp.ss};
}
return dp[pos];
}
int getSizes(int pos, int par = 0) {
vis[pos] = 1;
for (auto [a, b] : paths[pos]) {
if (a == par) continue;
sizes[pos] = max(sizes[pos], b + getSizes(a, pos));
}
return sizes[pos];
}
VI findCentroid(int pos, int par = 0, int pre = 0) {
int suf = len - pre;
for (auto [a, b] : paths[pos]) {
if (a == par) continue;
int x = pre+b, y = sizes[a];
if (max(pre, suf) > max(x, y)) return findCentroid(a, pos, pre+b);
}
return {pos, pre, suf};
}
VI getCentroid(int pos) {
len = getSizes(pos);
return findCentroid(pos);
}
int travelTime(int _N, int _M, int _L, int _A[], int _B[], int _T[]) {
n = _N;
m = _M;
L = _L;
vector <PII> pts;
for (int i = 0; i < _M; i++) {
paths[_A[i]+1].pb({_B[i]+1, _T[i]});
paths[_B[i]+1].pb({_A[i]+1, _T[i]});
}
for (int i = 1; i <= n; i++) {
if (vis[i]) continue;
PII tmp = getFarthest(i);
VI point = getCentroid(tmp.ss);
if (point[1] < point[2]) swap(point[1], point[2]);
pts.pb({point[1], point[2]});
// cout << i-1 << ": " << point[0]-1 << ' ' << point[1] << ' ' << point[2] << '\n';
}
// sort(ALL(pts), [&](auto&a, auto&b) {
// return max(a.ff, a.ss) < max(b.ff, b.ss);
// });
sort(ALL(pts));
n = pts.size();
for (int i = n-2; i >= 0; i--) {
// for (int j = 0; j < n; j++)
// cout << pts[j].ff << ',' << pts[j].ss << ' '; cout << '\n';
PII&a = pts[n-1];
PII&b = pts[n-2];
if (a.ff > a.ss) swap(a.ff, a.ss);
if (b.ff > b.ss) swap(b.ff, b.ss);
a.ff = max(a.ff, b.ss+L);
}
// cout << pts[n-1].ff+pts[n-1].ss << '\n';
return pts[n-1].ff+pts[n-1].ss;
}
