#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 300005;
ll n , m , au[300005] , av[300005] , aw[300005];
ll u , v , w , A;
vector<pair<ll, pair<ll , ll> > > adj[300005];
ll d1[300005] , dn[300005] , f[300005] , par[300005] , path[300005] , son[300005];
multiset<pair<ll , ll>> S;
vector<ll> B[300005] , T[300005];
void q(ll x){
f[x] = 1;
for(auto y : adj[x]){
//cout << "h";
auto it = S.find({dn[y.first] + y.second.first + d1[x] , y.second.second});
if(f[y.first]) S.erase(it);
else S.insert({dn[x] + y.second.first + d1[y.first] , y.second.second});
}
}
void dfs(int u , int p){
if(path[u]) son[u] = u;
else son[u] = son[p];
T[son[u]].emplace_back(u);
for(int v : B[u]) dfs(v , u);
}
main (){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> n >> m;
for(int i =0; i <m; ++i) cin >> au[i] >> av[i] >> aw[i];
for(int i = m - 1; ~i; --i){
u = au[i] , v = av[i] , w= aw[i];
adj[u].push_back({v , {w , A}});
adj[v].push_back({u , {w , A}});
A = max(A , w);
//cout << "j";
}
for(int i = 1; i <= n; ++i) d1[i] = dn[i] = 1e18;
d1[1] = 0;
dn[n] = 0;
priority_queue<pair<ll , ll> > pq;
pq.push({0 , 1});
while(pq.size()){
auto T = pq.top(); pq.pop();
u = T.second , w = -T.first;
if(f[u])continue;
f[u] = 1;
for(auto e : adj[u]){
v = e.first;
if(!f[v] && d1[v] > w + e.second.first){
par[v] = u;
d1[v] = w + e.second.first;
pq.push({-d1[v] , v});
}
}
//cout << "k";
}
for(int i = 1; i <= n; ++i)f[i] = 0;
//memset(f , 0 ,sizeof(f));
pq.push({0, n});
while(pq.size()){
auto T = pq.top(); pq.pop();
u = T.second , w = -T.first;
if(f[u])continue;
f[u] = 1;
for(auto e : adj[u]){
v = e.first;
if(!f[v] && dn[v] > w + e.second.first){
dn[v]= w + e.second.first;
pq.push({-dn[v] , v});
}
}
//cout << "l";
}
ll X = n;
while(1){
path[X] = 1;
if(X == 1) break;
X = par[X];
//cout << "n";
}
for(int i = 1; i <= n; ++i)B[par[i]].emplace_back(i);
dfs(1 , 0);
for(int i = 1; i <= n; ++i) f[i] =0;
ll s = n;
ll ans = d1[n];
//cout << "ka";
ll k;
while(1){
//cout << "ha";
if(s == 1)break;
for(ll v : T[s]) q(v);
s = par[s];
k = S.begin()->first + S.begin()->second;
auto i = S.begin();
++i;
if(i != S.end()) k =min(k , i->first);
ans = max(ans , k);
}
cout << ans;
kill(1);
}
Compilation message
Aesthetic.cpp:26:1: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
26 | main (){
| ^~~~
Aesthetic.cpp: In function 'int main()':
Aesthetic.cpp:104:11: error: too few arguments to function 'int kill(__pid_t, int)'
104 | kill(1);
| ^
In file included from /usr/include/c++/10/csignal:42,
from /usr/include/x86_64-linux-gnu/c++/10/bits/stdc++.h:43,
from Aesthetic.cpp:1:
/usr/include/signal.h:112:12: note: declared here
112 | extern int kill (__pid_t __pid, int __sig) __THROW;
| ^~~~
