Submission #530658

#	Time	Username	Problem	Language	Result	Execution time	Memory
530658		SlavicG	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	438 ms	23872 KiB

commuter_pass

#include "bits/stdc++.h"
using namespace std;
 
#define ll long long
 
#define       forn(i,n)              for(int i=0;i<n;i++)
#define          all(v)              v.begin(), v.end()
#define         rall(v)              v.rbegin(),v.rend()
 
#define            pb                push_back
#define          sz(a)               (int)a.size()

#define int long long

const int N = 2e5 + 10;
vector<pair<int, int>> adj[N];

ll ans = LLONG_MAX;
int n, m, s, t, a, b;
vector<int> order;
vector<ll> dijkstra(int a) {
    order.clear();
    priority_queue<pair<int,int>> q;
    vector<int> dist(n, (ll)1e18);
    vector<bool> vis(n, false);
    dist[a] = 0;
    q.push({0, a});
    while(!q.empty()) {
        int u = q.top().second;
        q.pop();
        if(vis[u]) continue;
        vis[u] = true;
        order.pb(u);
        for(auto x: adj[u]) {
            int w = x.second, v = x.first;
            if(dist[v] >= dist[u] + w) {
                dist[v] = dist[u] + w;
                q.push({-dist[v], v});
            }
        }
    }
    return dist;
}

vector<ll> distA, distB, distS, distT;

void solve() {
    cin >> n >> m >> s >> t >> a >> b;  --s, --t, --a, --b;

    for(int i = 0;i < m; ++i) {
        int u, v, c;
        cin >> u >> v >> c; --u, --v;
        adj[u].pb({v, c});
        adj[v].pb({u, c});
    }

    distA = dijkstra(a), distB = dijkstra(b);
    distS = dijkstra(s), distT = dijkstra(t);
    ans = distA[b];
    dijkstra(s);


    vector<int> dp(n, (ll)1e18);
    for(int node: order) {
        dp[node] = distA[node];
        for(auto f : adj[node]) {
            int v = f.first, w = f.second; 

            if(distS[v] + w == distS[node] && distS[v] + w + distT[node] == distS[t]) {
                dp[node] = min(dp[node], dp[v]);
            }
            ans = min(ans, dp[node] + distB[node]);
        }
    }

    dp.assign(n, (ll)1e18);

    for(int node: order) {
        dp[node] = distB[node];
        for(auto f: adj[node]) {
            int v = f.first, w = f.second; 
            if(distS[v] + w == distS[node] && distS[v] + w + distT[node] == distS[t]) {
                dp[node] = min(dp[node], dp[v]);
            }
            ans = min(ans, dp[node] + distA[node]);
        }
    }

    cout << ans << "\n";
} 
 
int32_t main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int t = 1;
    //cin >> t;
    while(t--) {
        solve();
    }
}

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