Submission #705836

#	Time	Username	Problem	Language	Result	Execution time	Memory
705836		noedit	Aesthetic (NOI20_aesthetic)	C++17	38 / 100	576 ms	49184 KiB

Aesthetic

#include <bits/stdc++.h>
//#include <quadmath.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#define sz(x) (int)x.size()
//#define sqr(x) x*x
//#pragma GCC optimize("-O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx,avx2,tune=native")
//#pragma GCC optimize("unroll-loops")
//#pragma GCC optimize("no-stack-protector")
//#pragma GCC optimize("fast-math")
using namespace std;
//using namespace __gnu_pbds;

#define int long long
//#define ld long double
//template <class T> using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
typedef long long ll;

const int INF = 1e18;

vector<vector<pair<int, int> > > g;

vector<int> es;
vector<int> tin, go;

vector<ll> suff;
vector<bool> used;
vector<ll> d1, dn;

int timer = 0;

bool flag = 0;

void dfs(int v, int p, ll x)
{
    used[v] = 1;
    tin[v] = go[v] = timer++;
    for (auto&[u, ind] : g[v])
    {
        if (p == u) continue;
        if (min(d1[v] + dn[u], d1[u] + dn[v]) + es[ind] >= x) continue;
        if (used[u])
        {
            go[v] = min(go[v], tin[u]);
        }
        else
        {
            dfs(u, v, x);
            go[v] = min(go[v], go[u]);
            if (go[u] > tin[v] && min(d1[v] + dn[u], d1[u] + dn[v]) + es[ind] + suff[ind + 1] >= x)
            {
                flag = 1;
            }
        }
    }
}

bool f(ll x)
{
    flag = 0;
    timer = 0;
    fill(tin.begin(), tin.end(), 0);
    fill(go.begin(), go.end(), INF);
    fill(used.begin(), used.end(), 0);
    dfs(0, -1, x);
    return flag || tin.back() == 0;
}

void dijkstra(int s, vector<ll>& dist)
{
    fill(dist.begin(), dist.end(), 1e18);
    set<pair<ll, int> > st;
    st.insert({0, s});
    dist[s] = 0;
    while (!st.empty())
    {
        auto [d, v] = *st.begin();
        st.erase(st.begin());
        for (auto&[u, ind] : g[v])
        {
            ll w = es[ind];
            if (dist[u] > dist[v] + w)
            {
                st.erase({dist[u], u});
                dist[u] = dist[v] + w;
                st.insert({dist[u], u});
            }
        }
    }
}

void solve()
{
    int n, m;
    cin >> n >> m;
    es.resize(m);
    suff.resize(m + 1);
    g.resize(n);
    tin.resize(n);
    d1.resize(n);
    dn.resize(n);
    go.resize(n);
    used.resize(n);
    for (int i = 0; i < m; i++)
    {
        int x, y, z;
        cin >> x >> y >> z;
        x--; y--;
        g[x].push_back({y, i});
        g[y].push_back({x, i});
        es[i] = z;
    }
    suff[m - 1] = es[m - 1];
    for (int i = m - 2; i >= 0; i--)
    {
        suff[i] = max(suff[i + 1], es[i]);
    }

    dijkstra(0, d1);
    dijkstra(n - 1, dn);

    ll lt = d1[n - 1], rt = d1[n - 1] + suff[0] + 1;
    while (rt - lt  > 1)
    {
        ll mid = (lt + rt) >> 1;
        if (f(mid))
        {
            lt = mid;
        }
        else
        {
            rt = mid;
        }
    }
    cout << lt;
}

signed main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    int t;
    t = 1;
    while (t--)
    {
        solve();
    }
    return 0;
}


/*
4 4
1 2 1 3
1 1
1 2
1 3
1 4
*/

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