Submission #285010

#	Time	Username	Problem	Language	Result	Execution time	Memory
285010		3zp	Aesthetic (NOI20_aesthetic)	C++14	51 / 100	870 ms	77148 KiB

Aesthetic

#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int N = 500009;
vector<pair<ll, pair<ll, ll > > > v[N];
vector<ll> T[N];
ll d1[N],dn[N], f[N], g[N],ea[N],eb[N],ec[N], par[N],path[N],wh[N];
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});
    }
}
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) continue;
        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});
            }
        }
    }
    vector<pair<ll,ll> > W;
    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.push_back({d1[i], i});
    }
    sort(W.begin(), W.end());
    for(ll i = 0; i < W.size(); i++){
        ll x = W[i].second;
        if(path[x]) wh[x] = x;
        else wh[x] = wh[par[x]];
        T[wh[x]].push_back(x);
    }
    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:19:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
   19 | main(){
      |      ^
Aesthetic.cpp: In function 'int main()':
Aesthetic.cpp:85:21: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int>, std::allocator<std::pair<long long int, long long int> > >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |     for(ll i = 0; i < W.size(); i++){
      |                   ~~^~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 7 / 7
• Subtask 4: 15 / 15
• Subtask 5: 16 / 16
• Subtask 6: 0 / 22
• Subtask 7: 0 / 27