Submission #899274

#	Time	Username	Problem	Language	Result	Execution time	Memory
899274		aykhn	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	274 ms	36736 KiB

commuter_pass

#include <bits/stdc++.h>
 
// author: aykhn
 
using namespace std;
typedef long long ll;
 
#define all(v) v.begin(), v.end()
#define pii pair<int, int>
#define mpr make_pair
#define eb emplace_back
#define pb push_back
#define ts to_string
#define fi first
#define se second
#define ins insert
#define int ll
#define inf 0x3F3F3F3F
#define infll 0x3F3F3F3F3F3F3F3FLL
#define bpc __builtin_popcount
 
const int MXN = 1e5 + 5;
 
int dist[2][MXN];
int d[MXN];
int mn1[MXN], mn2[MXN];
vector<array<int, 2>> adj[MXN];
vector<int> par[MXN];
vector<int> g[MXN], o;
int used[MXN];
 
void dijk(int s, int id)
{
    for (int i = 0; i < MXN; i++) dist[id][i] = infll;
    priority_queue<array<int, 2>, vector<array<int, 2>>, greater<array<int, 2>>> pq;
    dist[id][s] = 0;
    pq.push({0, s});
    while (!pq.empty())
    {
        array<int, 2> f = pq.top();
        pq.pop();
        if (f[0] > dist[id][f[1]]) continue;
        for (const array<int, 2> &v : adj[f[1]])
        {
            if (dist[id][v[0]] > f[0] + v[1])
            {
                dist[id][v[0]] = f[0] + v[1];
                pq.push({dist[id][v[0]], v[0]});
            }
        }
    }
}
 
void dfs(int a)
{
    used[a] = 1;
    for (int v : par[a])
    {
        g[v].pb(a);
        if (used[v]) continue;
        dfs(v);
    }
}
 
void dfs1(int a)
{
    used[a] = 1;
    for (int v : g[a])
    {
        if (used[v]) continue;
        dfs1(v);
    }
    o.pb(a);
}
 
signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr);
    int n, m, s, t, u, v;
    cin >> n >> m >> s >> t >> u >> v;
    while (m--)
    {
        int u, v, w;
        cin >> u >> v >> w;
        adj[u].pb({v, w});
        adj[v].pb({u, w});
    }
    dijk(u, 0);
    dijk(v, 1);
    for (int i = 0; i < MXN; i++) d[i] = mn1[i] = mn2[i] = infll;
    priority_queue<array<int, 2>, vector<array<int, 2>>, greater<array<int, 2>>> pq;
    d[s] = 0;
    pq.push({0, s});
    while (!pq.empty())
    {
        int f = pq.top()[1];
        int w = pq.top()[0];
        pq.pop();
        if (w > d[f]) continue;
        for (const array<int, 2> &v : adj[f])
        {
            if (d[v[0]] > w + v[1])
            {
                d[v[0]] = w + v[1];
                par[v[0]].clear();
                par[v[0]].pb(f);
                pq.push({d[v[0]], v[0]});
            }
            else if (d[v[0]] == w + v[1]) par[v[0]].pb(f);
        }
    }
    for (int i = 0; i < MXN; i++) used[i] = 0;
    dfs(t);
    for (int i = 0; i < MXN; i++) used[i] = 0;
    dfs1(s);
    reverse(all(o));
    int res = infll;
    for (int x : o)
    {
        mn1[x] = min(mn1[x], dist[0][x]);
        mn2[x] = min(mn2[x], dist[1][x]);
        res = min(res, mn1[x] + dist[1][x]);
        res = min(res, mn2[x] + dist[0][x]);
        for (int v : g[x])
        {
            mn1[v] = min(mn1[v], mn1[x]);
            mn2[v] = min(mn2[v], mn2[x]);
        }
    }
    cout << min(dist[0][v], res) << '\n';
}

• Subtask 1: 16 / 16
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 45 / 45