#include "dreaming.h"
#include <bits/stdc++.h>
#define MAX 200001
#define INF INT_MAX
#define MOD 1000000007
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define ins insert
#define ff first
#define ss second
#define gett(x,m) get<m>(x)
#define all(a) a.begin(),a.end()
#define lb(a,b) lower_bound(all(a),b)
#define ub(a,b) upper_bound(all(a),b)
#define sortv(a) sort(all(a))
#define sorta(a,sz) sort(a,a+sz)
#define inputar(a,b){\
for(long long i=0;i<b;i++){\
cin >> a[i];\
}\
}
#define inputvec(a,b){\
for(long long i=0;i<b;i++){\
ll num;\
cin >> num;\
a.pb(num);\
}\
}
#define outputar(a,b){\
for(long long i=0;i<b;i++){\
cout << a[i] << " ";\
}\
cout << "\n";\
}
#define outputvec(a){\
for(auto x:a){\
cout << x << " ";\
}\
cout << "\n";\
}
#define reset(a,n,v){\
for(long long i=0;i<n;i++){\
a[i]=v;\
}\
}
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef tuple<ll,ll,ll> tll;
typedef pair<ll,ll> pll;
typedef pair<long long,long long> pii;
typedef double db;
typedef long double ldb;
inline void USACO(string filename){
freopen((filename+".in").c_str(),"r",stdin);
freopen((filename+".out").c_str(),"w",stdout);
}
ll h;
vector<bool> used;
vector<long long> dist;
vector <long long> dist2;
vector<long long> maxdist1;
vector<pair<pii,pii>> maxdist;
vector<vector<pii>> g;
vector<long long> b;
vector<long long> e;
void dfs(long long v,long long prev){
e.pb(v);
used[v]=true;
for(auto x:g[v]){
if(x.ff==prev){
continue;
}
dist[x.ff]=dist[v]+x.ss;
dfs(x.ff,v);
}
}
void dfs4(long long v,long long prev){
for(auto x:g[v]){
if(x.ff==prev){
continue;
}
dist2[x.ff]=dist2[v]+x.ss;
dfs4(x.ff,v);
}
}
void dfs1(long long v,long long prev){
used[v]=true;
maxdist1[v]=dist[v];
for(auto x:g[v]){
if(x.ff==prev){
continue;
}
dfs1(x.ff,v);
maxdist1[v]=max(maxdist1[v],maxdist1[x.ff]);
}
}
void dfs2(long long v,long long prev){
used[v]=true;
for(auto x:g[v]){
if(x.ff==prev){
continue;
}
if(maxdist1[x.ff]>maxdist[v].ff.ff){
maxdist[v].ss=max(maxdist[v].ss,maxdist[v].ff);
maxdist[v].ff=mp(maxdist1[x.ff],x.ff);
}
else if(maxdist1[x.ff]>maxdist[v].ss.ff){
maxdist[v].ss=mp(maxdist1[x.ff],x.ff);
}
dfs2(x.ff,v);
}
}
void dfs3(long long v,long long prev){
long long h1=0;
h1=max(h1,maxdist1[v]-dist[v]);
if(prev!=-1){
pair<pii,pii> p1=maxdist[prev];
pii p2,p3;
p2=p1.ff;
p3=p1.ss;
b[v]=b[prev]+dist[v]-dist[prev];
if(p2.ss!=v && p2.ff!=-INF){
b[v]=max(b[v],p2.ff+dist[v]-dist[prev]);
}
else if(p3.ff!=-INF){
b[v]=max(b[v],p3.ff+dist[v]-dist[prev]);
}
h1=max(h1,b[v]);
}
h=min(h,h1);
used[v]=true;
for(auto x:g[v]){
if(x.ff==prev){
continue;
}
dfs3(x.ff,v);
}
}
long long travelTime(long long N, long long M, long long L, long long A[], long long B[], long long T[]) {
long long res;
g.resize(N);
dist.resize(N,0);
used.resize(N,0);
dist2.resize(N,0);
b.resize(N,0);
pair<pii,pii> a;
a=mp(mp(-INF,-INF),mp(-INF,-INF));
maxdist.resize(N,a);
maxdist1.resize(N);
for(long long i=0;i<M;i++){
g[A[i]].pb(mp(B[i],T[i]));
g[B[i]].pb(mp(A[i],T[i]));
}
long long maxd=0;
for(long long i=0;i<N;i++){
if(!used[i]){
e.clear();
dfs(i,-1);
long long maxd1=0;
long long maxd2=0;
long long ind=0;
for(auto x:e){
if(dist[x]>maxd1){
maxd1=dist[x];
ind=x;
}
}
dfs4(ind,-1);
for(auto x:e){
maxd2=max(maxd2,dist2[x]);
}
maxd=max(maxd,maxd2);
}
}
for(long long i=0;i<N;i++){
used[i]=false;
}
for(long long i=0;i<N;i++){
if(!used[i]){
dfs1(i,-1);
}
}
for(long long i=0;i<N;i++){
used[i]=false;
}
for(long long i=0;i<N;i++){
if(!used[i]){
dfs2(i,-1);
}
}
for(long long i=0;i<N;i++){
used[i]=false;
}
vector<long long> c;
for(long long i=0;i<N;i++){
if(!used[i]){
h=INF;
dfs3(i,-1);
c.pb(h);
}
}
sortv(c);
reverse(all(c));
if(c.size()==1){
res=c[0];
}
else{
res=c[0]+c[1]+L;
}
if(c.size()>2){
res=max(res,c[1]+c[2]+2*L);
}
res=max(maxd,res);
return res;
}
/*
long long main(){
long long n,m,k;
cin >> n >> m >> k;
long long A[m],B[m],T[m];
for(long long i=0;i<m;i++){
cin >> A[i] >> B[i] >> T[i];
}
cout << travelTime(n,m,k,A,B,T);
}
*/
Compilation message
/usr/bin/ld: /tmp/cc5USAtS.o: in function `main':
grader.c:(.text.startup+0xd1): undefined reference to `travelTime'
collect2: error: ld returned 1 exit status
