This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include<bits/stdc++.h>
#define ll long long
using namespace std;
vector<pair<ll, pair<ll, ll > > > v[300009];
vector<ll> T[300009],W[300009];
ll d1[300009],dn[300009], f[300009], g[300009],ea[300009],eb[300009],ec[300009], par[300009],path[300009],wh[300009];
multiset<pair<ll,ll> > S;
void ad(ll x){
g[x] = 1;
for(auto E : v[x]){
ll y = E.first, l = E.second.first, u= E.second.second;
auto it= S.find({dn[y] + l + d1[x], u});
if(g[y] == 1) S.erase(it);
if(g[y] == 0) S.insert({dn[x] + l + d1[y], u});
}
}
void dfs(int x, int p){
if(path[x]) wh[x] = x;
else wh[x] = wh[p];
T[wh[x]].push_back(x);
for(int y : W[x]){
dfs(y, x);
}
}
ll A = 0;
main(){
ios_base::sync_with_stdio(false);
cin.tie(0);
ll n, m;
cin >> n >> m;
for(ll i = 0; i < m; i++){
cin>>ea[i]>>eb[i]>>ec[i];
}
for(ll i = m-1; i >= 0; i--){
ll a = ea[i], b = eb[i], c = ec[i];
if(a != b){
v[a].push_back({b, {c,A}});
v[b].push_back({a, {c,A}});
}
A = max(A, c);
}
for(ll i = 1; i <= n; i++){
d1[i] = 1e18;
dn[i] = 1e18;
}
d1[1] = 0;
dn[n] = 0;
priority_queue<pair<ll, ll> > q;
q.push({0, 1});
while(q.size()){
ll x = q.top().second;
q.pop();
if(f[x]) continue;
f[x] = 1;
for(auto E: v[x]){
ll y = E.first, l = E.second.first;
if(!f[y] && d1[y] > d1[x] + l){
d1[y] = d1[x] + l;
par[y] = x;
q.push({-d1[y], y});
}
}
}
q.push({0, n});
for(ll i = 1; i <= n; i++)
f[i] = 0;
while(q.size()){
ll x = q.top().second;
q.pop();
if(f[x]) continue;
f[x] = 1;
for(auto E: v[x]){
ll y = E.first, l = E.second.first;
if(!f[y] && dn[y] > dn[x] + l){
dn[y] = dn[x] + l;
q.push({-dn[y], y});
}
}
}
ll ans = d1[n];
ll X = n;
while(1){
path[X] = 1;
if(X == 1) break;
X = par[X];
}
for(ll i = 1; i <= n; i++){
W[par[i]].push_back(i);
}
dfs(1,0);
ll x = n;
while(1){
for(ll y : T[x])
ad(y);
if(x == 1) break;
x = par[x];
if(S.size() == 0) continue;
ll U = S.begin()->first + S.begin()->second;
auto it = S.begin();
it++;
if(it != S.end()) U = min(U, it->first);
ans = max(ans, U);
}
cout<<ans<<endl;
}
Compilation message (stderr)
Aesthetic.cpp:26:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
26 | main(){
| ^
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