#include "dreaming.h"
#include <bits/stdc++.h>
#define ll long long
using namespace std;
ll rad;
vector<vector<pair<ll, ll>>> adj;
vector<bool> vis, dvis;
vector<ll> diapath, diaedges;
vector<ll> parent;
pair<ll, ll> get_furthest(ll node){
dvis = vis;
queue<pair<ll, ll>> q;
ll dist = 0, ret = 0;
q.push({node, 0});
while(!q.empty()){
pair<ll, ll> val = q.front();
q.pop();
for(pair<ll, ll> i : adj[val.first]){
if(!dvis[i.first]){
parent[i.first] = val.first;
q.push({i.first, i.second + val.second});
if(i.second + val.second > dist){
ret = i.first;
dist = i.second + val.second;
}
}
}
dvis[val.first] = true;
}
return {ret, dist};
}
ll diameter(ll node, ll N){
diapath.clear(), diaedges.clear();
ll a = 0, b = 0, dist = 0, p;
pair<ll, ll> dia;
a = get_furthest(node).first;
dia = get_furthest(a);
b = dia.first;
p = b;
while(p != a){
diapath.push_back(p);
for(pair<ll, ll> i : adj[p]) if(i.first == parent[p]) diaedges.push_back(i.second);
p = parent[p];
}
diapath.push_back(a);
vis = dvis;
return dia.second;
}
int travelTime(int N, int M, int L, int A[], int B[], int T[]) {
adj.resize(N), parent.resize(N);
ll bigcenter = 0, maxdia = 0;
vector<ll> centers;
for(ll i = 0; i < M; i++){
adj[A[i]].push_back({B[i], T[i]});
adj[B[i]].push_back({A[i], T[i]});
}
vis.assign(N, false), dvis = vis;
for(ll i = 0; i < N; i++){
if(!vis[i]){
ll dialength = diameter(i, N);
ll c = i, p = 0, mindist = dialength;
if(dialength > 0){
for(ll j = 0; j < diapath.size(); j++){
if(max(p, dialength - p) < mindist){
c = diapath[j];
mindist = max(p, dialength - p);
}
if(j < diaedges.size()) p += diaedges[j];
}
p = 0;
for(ll j = diapath.size()-1; j >= 0; j--){
if(max(p, dialength - p) < mindist){
c = diapath[j];
mindist = max(p, dialength - p);
}
if(j-1 < diaedges.size()) p += diaedges[j-1];
}
}
if(dialength > maxdia){
bigcenter = c;
maxdia = dialength;
}
centers.push_back(c);
}
}
for(ll i : centers){
if(i != bigcenter){
adj[i].push_back({bigcenter, L});
adj[bigcenter].push_back({i, L});
}
}
vis.assign(N, false);
return diameter(0, N);
}
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